
} 



W M. J. C. DULANY COMPANY 
BALTIMORE 




Class _Qi^i^ 

Book _;fii 

Copyright K^ 

COPYRIGHT DEPOSIT. 





Bones in the hand and wrist. 
(From an X ray photograph.) 



MARYLAND PHYSIOLOGY SERIES 



SCHOOL 
PHYSIOLOGY 






>^ > 1 ? ' » 



WM. J. C. DULANY COMPANY 

BALTIMORE 



Q"?^*^ 

.0^^ 



LIBRARY nf CONGRESS 
Two Copies Received 

JUN 30 1904 

^ OooyrJirht Entry 

VIMaJ^ to- lc\o^ 
CLASS ^ XXo. Na 

^ c -) ^ 

COPY B 



By permission of the publishers, copyright material from 
Overton's Apphed Physiology, Advanced Grade, copyright, 
1897, by American Book Company, has been used in this book. 



Copyright, 1904, by 
Wm. J. C. DuLAxNY Company 



PREFACE 

This text-book of Applied Physiology was suggested by 
a series of popular lectures in which the author presented 
the essential principles of physiology about which a physi- 
cian is consulted daily. His explanations of many common 
facts were entirely novel to the auditors, and on investiga- 
tion it was found that the school text-books were silent 
upon many of these points, especially in regard to the cells, 
where the essential vital functions of the body are carried 
on. Throughout this book the fact that the cells are the 
units in which life exists and acts is emphasized. 

The author has endeavored to include all the useful 
points of the older text-books, and to add such new matter 
as the recent progress of physiological and hygienic 
science demands. He has avoided technical terms, and 
has sought to express the truths in simple language such 
as he would use in instructing a mother as to the nature 
of the sickness of her child. 

The subject of alcohol is discussed in all its aspects. 
Its evil effects are not exaggerated ; but the alleged 
good from the use of strong drink is contrasted with its 
dangers in a judicial manner, which appeals to men far 
more effectively than dogmatic abuse. The relation of 
alcoholic indulgence to other forms of intemperance, as 
excessive sugar eating, is also explained. 

The essential act of respiration is oxidation within the 
cells. The relation of oxidation to the disappearance of 

5 



6 PREFACE 

food, to the production of waste matters, and to the 
development of heat and force, is dwelt upon throughout 
the book. 

Many of the demonstrations at the ends of chapters are 
new. All can be performed without the purchase of a 
single article of apparatus, except a microscope. The 
prepared microscopic specimens can be borrowed from a 
physician. 

Most of the cuts are entirely new, and have been 
sketched by the author from actual specimens. The 
microscopic appearances of the tissues are especially illus- 
trated. In each cut the illustration of a point, rather than 
artistic effect, has been the end in view. 

The chapter on Repair of Injuries is an entirely new 
feature in a school text-book. How the body restores 
its natural functions after injury is as practical and simple 
a subject as how it sustains itself in health. 

The author wishes to express his gratitude to his friend 
and instructor. Professor William H. Porter, of the New 
York Post Graduate Medical School, who has given his 
valuable counsel and encouragement throughout the entire 
preparation of the work; to Dr. W. E. Gordon, Principal 
of the Patchogue High School, for his suggestions in 
adapting the work to the practical needs of the pupils; 
and to Dr. Thomas E. Satterthwaite, ex-vice president of 
the New York Post Graduate Medical School, and Dr. 
William Pepper, M.D., LL.D., ex-provost of the Univer- 
sity of Pennsylvania, for their kind criticisms of the proof 
sheets. Thanks are also due Professor J. O. Lansing 
for valuable pedagogical suggestions, and to Mr. Robert 
Cruger for suggestions and aid in the illustrations. 

Patchogue, N.Y. 



CONTENTS 



I. Living Bodies and Cells 

II. Ele-Ments of the Body . 

III. Oxidation 

IV. Fermentation and Alcohol . 

V. Digestion of Food in the Mouth . 

VI. Stomach Digestion . 

VII. Abnormal Action of the Stomach 

VIII. Intestinal Digestion 

IX. Absorption and Assimilation . 

X. Alcohol and Digestion . 

XI. Digestion in Lower Animals . 

XII. Animal Food .... 

XIII. Vegetable Food 

XIV. Quantity of Food required . 
XV. Drinking Water 

XVI. Narcotics 

XVII. Drugs and Poisons . 

XVIII. The Blood .... 

XIX. The Heart .... 

XX. The Flow of Blood in the Body 

XXI. Regulation of the Flow of Blood 

7 



PAGE 

9 

22 

33 
41 
51 
66 

74 
79 



104 
107 
120 
131 
135 
140 
148 
156 
162 
172 
185 



8 . CONTENTS 

CHAPTER PAGE 

XXII. The Lungs 192 

XXIII. Respiration of the Tissues .... 206 

XXIV. The Air and Ventilation 220 

XXV. Heat and Clothing 233 

XXVI. Excretion and Sewage 248 

XXVII. The Skin and Bathing . . = . . 256 

XXVIII. Nerves 266 

XXIX. The Spinal Cord 276 

XXX. The Sympathetic Nervous System . . . 284 

XXXI. The Brain 289 

XXXII. Influences which affect the Mind . . . 305 

XXXIII. Effects of Narcotics upon the Mind . -315 

XXXIV. Taste, Smell, and Hearing .... 323 
XXXV. The Eye .333 

XXXVI. The Voice . . 349 

XXXVII. Bones . .357 

XXXVIII. Joints 364 

XXXIX. Muscles 371 

XL. Bacteria and Disease . . . . . , 382 

XLI. Repair of Injuries ...... 393 

Glossary o . 401 

Index „ . o 425 



APPLIED PHYSIOLOGY 

CHAPTER I 

LIVING BODIES AND CELLS 

1. What physiology is. — The world is composed of 
living bodies and lifeless matter. In living bodies there 
is a constant change, in which particles become lifeless 
and are thrown off, while, at the same time, a process of 
creation is going on by which lifeless matter is given life. 
This constant destruction and renewal of the particles of 
the body constitutes life. 

The science which tells of the structure of living bodies 
is Aiuxtomy ; that w^hich tells of their zvorking is PJiysi- 
ology ; and that which tells how to keep living bodies in 
good working order is Hygiene. The term pJiysiology 
often includes anatoniy and Jiygiene. 

Some processes in man's physiology were discovered 
only by studying the lower animals ; and others, by 
observing plants. In fact, it is by studying the work- 
ings of lower forms of life that most of our knowledge 
of the working of man's life has been gained. The 
physiology of vegetables and animals teaches the physi- 
ology of man, because man embodies the characteristics 
of lower forms of life. During the course of ages life de- 

9 



lO APPLIED PHYSIOLOGY 

veloped through vegetables and lower animals up to its 
highest point in the most perfect animal, — man. 

2. The ameba. — One of the simplest animals lives in 
stagnant water and is called the anteba. It is only a lump 
of jelly about ^^Vo" °^ ^^ vno)^ in diameter, yet it is a com- 
plete animal, for it moves, and eats, and grows, and pro- 
duces other a^nebas. It has no arms, or legs, or head, but 
all parts of its body seem very nearly alike. It puts out 
little fingers from its body and then rolls its whole body 
into the fingers. In this way it is continually rolling about. 
When it finds a particle of food it wraps itself around it ■ 
just as a baker rolls a mass of bread dough around a 




An ameba, sketched at intervals of ten seconds ( x 400) . 

raisin. That part of the body which is in contact with 
the food digests as much as is needed, and then unwraps 
itself away from the waste. It has no choice as to what 
part of its body it shall use for any given purpose. But 
man uses each part of his body for only definite purposes. 
He has arms which get food, a mouth which eats it, and a 
stomach which digests it. The arms cannot eat food, 
neither can the mouth digest it, but each part does only 
its own kind of work. 

3. Man like an ameba. — Each part of a man's body is 
made of multitudes of living beings, each of which eats 
and grows like an ameba. Each tiny being is called a 
cell. One collection of cells forms the ski7i, another the 
muscles of the arm, and another the stomachy and so on 



LIVING BODIES AND CELLS 



II 




through the body. Each collection does its own work, 
without interfering with the others. The cells work 
together like a well-trained army, so 
that we do not feel the workings of 
each separate cell. If a collection is 
out of order, the person is sick. 

4. Cells. — Cells are of various 
shapes, according to the work they 

have to do. They are from 5 J^ o ^o piants and animairfound 
jIq of an inch in length. Each cell in stagnant water, each con- 
. ... , . 1 . ,1 1 . 1 1 sistingofasinglecell(X20o). 

IS like thick jelly and is almost color- 
less. Near its center a small mass of slightly different 
composition may usually be distinguished. This central 

mass is called the micleiLs. 
The substance composing 
the cell is like the white of 
an Q,gg and is called proto- 
plasm. Although proto- 
plasm is 
transpar- 
ent and 
jellylike, 
yet under 
a micro- 
scope 
there ap- 
pears an interlacing series of beads and 
lines which suggest a structure as com- 
plex as that of the body itself. 

5. Connective tissue. — The cells are 
kept in place by a fine network of strong fibers called con- 
nective tissue. In some parts of the body, as on the outside 
of the muscles, it is thick and skinlike, but around each 




Cells from the human body ( x 200) . 

a A colored cell from the eye. 

b A white blood cell. 

c A connective tissue cell. 

d A cell from the lining of the mouth. 

e Liver cells. 

/ A muscle cell from the intestine. 




Diagram of the parts 
of a cell. 

a Nucleus. 

b Cell-body or proto- 
plasm. 

c Covering, generally 
absent in animal 
cells. 



12 APPLIED PHYSIOLOGY 

separate cell there are only enough fibers to keep the cell 
in place. Even these connective tissue fibers are the 
threadlike arms of very small cells set apart for the 
menial work of supporting other cells. 

6. Three tests of life. — We know that each cell is alive; 
for it moves, it takes in food, and it multiplies. 

(i) Motion. — Although each cell is held in place by the 
connective tissue, the tiny particles of its body are in con- 
stant motion, just as a boy's eyes and mouth and hands 
and feet may move, even if he sits still in a chair. Besides 
this continual motion of the particles within the cell, some 
cells show a greater motion, in which the cell as a whole 
takes part. Thus, a muscle cell becomes thicker and 
shorter when the muscle bends a joint. A white blood 
cell can force its way through the wall of the blood tube, 
and can wander about among the cells of the body. 

(2) Nutrition and Groivth. — The blood bathes the cells 
with food which does not resemble their protoplasm. Each 
cell takes in the food through any portion of its body, and, 
endowing it with life, makes it a part of itself. Thus each 
cell increases in size. 

(3) Reproduction. — During the period of growth of the 
body, there is a constant production of the cells ; for the 
man is composed of more cells than the child. Even in a 
full-grown man certain cells, as those of the skin, are con- 
stantly being shed and new ones formed. When a cell 
reaches mature life, the nucleus first divides into two parts, 
which separate from each other ; then the body 'of the cell 
divides between the two nuclei. Thus each cell becomes 
two cells, and each of the two exactly resembles the origi- 
nal cell, except that it is smaller at first ; but it soon grows 
to be as large as the original cell. All the peculiarities of 
the life of the first cell go on in each of the two. cells into 



LIVING BODIES AND CELLS 1 3 

which it divides ; and so we say that the new cell inherits 
the peculiarities of the parent. This process may be 
carried on very rapidly ; and a new cell may be produced, 
and itself become divided, in a few hours. 

Anything that moves, and eats, and reproduces itself by 
means of its own power, is alive ; and so the cells of the 
body are alive in the fullest sense of the term. 




Diagram of the division of a cell. 

7. Other distinctions between the living and the dead. — 

Many living bodies wi41 show some spontaneous movement in response 
to a prick or a blow, or other irritation. Certain causes, as a low tem- 
perature, may suspend the ability to respond to an irritation, but it will 
return when warmth is applied. A lifeless thing never puts forth effort, 
no matter how much it is irritated. 

Decay never occurs in cells while they live ; but after death disinte- 
gration soon begins, even if no outside power acts upon the cells. On 
the other hand, a body which has never been alive usually changes very 
slowly or not at all, unless acted upon by an outside power. 

8. Relation of cells. — In the body formed by the cells 
there exists a controlling spirit of life, whose nature is 
unknown. When all the cells are obedient to its influence 
the body as a whole is alive ; but if the cells are not 
obedient, the body as a whole is dead, although each 
separate cell may remain alive. For example, a blow 
upon the head may disturb this controlling influence so 
that it cannot tell the cells how to act. Then they instantly 
stop work, and the body drops dead. Yet each cell may 
remain alive for minutes or hours, just as each soldier may 
remain alive after an army has been disbanded. 



14 APPLIED PHYSIOLOGY 

9. Tissues. — While each cell eats, grows, and pro- 
duces other cells more or less independently of the rest, 
yet, Hke the members of a large family, each works for 
the benefit of all the others, and, in turn, is dependent 
upon them for things which it cannot do so well as they. 
Cells doing special kinds of work are collected in orderly 
groups called tissues. Six kinds of tissues are well 
marked, — 

(i) Muscular Tissue. — Groups of ribbonlike cells which 
have the power of moving the adjacent parts are found 
everywhere in the body, and form muscular tissue. This 
tissue is usually as abundant as all the rest of the tissues 
taken together. 

(2) Epithelial Tissue. — Covering all the surface of the 
body, and lining every cavity and tube which connects 
with the surface of the body, is a layer of firm cells which 
form epithelial tissue. It protects the underlying parts 
and manufactures all the various fluids of the body. 
From it, also, the hair and nails are produced. Epithelial 
tissue is abundant and important. 

(3) Nervous Tissue. — There are cells which control all 
the others. By means of their long, threadlike prolonga- 
tions they convey orders to every cell in the body. They 
and their prolongations form nervous tissue. 

(4) Connective Tissue. — Surrounding each cell, and 
holding it in place, are the extremely fine arms of small 
cells called comiective tissue {^^o. p. 11). Its amount varies 
greatly in different parts of the body and in different per- 
sons, but its total amount is always very large. In some 
parts of the body, as in the skin and lungs, there is a 
special kind of connective tissue which is very elastic, and 
gives to the parts their stretching properties. This tissue 
is called ''yellow elastic tissue^'' from its color. 



LIVING BODIES AND CELLS 1 5 

(5) Osseous Tissue. — A special form of connective 
tissue, in which enough lime is mixed to make it stiff, is 
called bofiy or osseous tissue. This tissue is rigid and 
strong so as to form a framework for the rest of the cells 
of the body. A somewhat similar tissue, containing little 
or no lime, is called eartilaginous tissue. It surrounds the 
jointed ends of bones and often becomes bone late in life. 

(6) Adipose Tissue. — Some connective tissue cells are 
arranged in microscopic pockets filled with oil or fat. 
This forms fatty or adipose tissue. Most of the fat in 
the body is stored in this way (see p. 25). 

10. The blood as a tissue. — Blood contains two kinds of 
cells, each of which has a special work to do. The fluid 
in which the cells float can become solid, and therefore 
blood is really a tissue. The lymph, which is mainly 
diluted blood, may also be considered a tissue. 

11. Other fluids in the body. — There are other fluids in 
the body which, while they contain a few cells, do not 
depend upon them for their properties or actions and so 
are not tissues. Into the digestive tube there are poured 
five fluids concerned in digestion, viz. : the saliva, the 
gastric juice, the pancreatic juice, the bile, and the intes- 
tinal juice. In order to carry off the waste products of 
the body two fluids, the perspiration and the iirine, are 
continually being formed, while water is given off in 
gaseous form by the breath. Three fluids are found in 
connection with the eye. Two, called the aqueous and 
the vitreous humors, distend the eyeball, and another, 
called tears, runs over its surface to wash away dirt. In- 
side the cavity of each joint is a thick fluid, Q2}\^^ synovia, 
which lubricates the surface of the bones within the mov- 
able joints. Lastly, milk is sometimes produced for the 
nourishment of the young, 



l6 APPLIED PHYSIOLOGY 

12. Organs. — In order to work to the best advantage, 
several kinds of tissues are usually associated together. 
Thus, the stomach, which digests food, is composed of 
miiscidar tissue which moves the food about, and epithelial 
tissue which pours out digestive fluids, and nervous tissue 
which presides over the process, while connective tissue 
binds the whole together. A collection of different tis- 
sues always arranged in a definite, compact shape for a 
special purpose, is called an organ. The stomach, intestine^ 
panc7^eas, and the liver are the four principal organs of 
digestion. The lungs are organs of respiration, the heart 
is an organ for the propulsion of blood. The kidneys anc 
skin are organs which get rid of waste matter, and the 
brain is the organ of thought. The term organ is also 
applied to many other parts of the body, but these are 
the principal ones. 

13. Systems. — Sometimes a definite series of tissues 
and organs are not arranged in compact form, but are 
scattered through the w^hole body. This forms a system. 
Thus the system of tubes formed of muscular and con- 
nective tissue in which the blood moves is called the 
circidatory system, while the heart is an organ in the cir- 
culatory system. In the same way the brain is an organ 
in the nervous system. The five main systems are the 
digestive, circidatory, respiratory, nervons, and excretory 
systems. In Physiology the action of the cells of each 
tissue, organ, and system is studied separately. The 
structure and arrangement of the cells of each tissue 
are studied by means of a microscope. 

14. The microscope. — In order to show even the largest 
cell, a compound microscope magnifying at least twenty 
times is needed ; while for ordinary use, one magnifying 
at least two hundred times is necessary. 



LIVING BODIES AND CELLS 



17 



A compound microscope consists of two lenses set in a 
movable tube. The lower lens is called the objective, and 
does the main part of the magnifying. It can easily be 
removed from the tube or swung aside, and another 
objective of different magnifying power substituted for it. 



COARSE ADJUSTMENT 




MIRROR 
LIGHTING 
SPECIMEN 



Compound microscope. 



The upper lens is called the eyepiece. It can be re- 
moved from the tube, and another substituted. Usually 
two or three objectives and two eyepieces of different 
magnifying powers are furnished with each microscope. 
A microscope is said to magnify as many diameters as 
the number of times it enlarges the breadth or diameter 

OV. PHYSIOL. — 2 



1 8 APPLIED PHYSIOLOGY 

of an object. Thus a microscope making a cell appear 
100 times as broad as it really is, is said to magnify lOO 
diameters. But the length and thickness are also magni- 
fied. So the surface of the cell is made lOO x lOO or 
10,000 times as large, while its bulk is 100 x 100 x 100 
or 1,000,000 times as large. A table accompanying each 
instrument tells the power of each combination of lenses. 

15. Arrangement of the light. — A small mirror placed at the 
lower part of the microscope throws light through the object, for other- 
wise there would not be sufficient light to spread over its magnified 
surface. The mirror can be tilted so as to catch the light from any 
direction. Objects usually show best when they are lighted only suf- 
ficiently to show their outlines. A stronger light may pass through 
extremely small objects so that they do not show at all. Each micro- 
scope usually has a device for varying the size of the aperture in the 
plate upon which the specimen rests, thus again regulating the amount 
of light. It is usually not best to use an amount of light which makes 
the field of view brilliant. 

16. Focusing. — The tube carrying the lenses can be moved up 
and down by means of a small wheel. Arranging the distance of the 
lens from the specimen is called focusing. An objective of high mag- 
nifying power must be much nearer to the specimen than one of low 
power. Thus an objective magnifying 500 diameters must be about 
Jq of an inch from the specimen, while one magnifying 50 diameters 
would be over half an inch distant. For high magnifying powers 
the focusing must be very exact. So a second wheel is provided 
which moves the tube very slowly. This wheel is called the fine ad- 
justment in distinction from the other wheel or coarse adjusti7ient. 
The finger of the observer should always be upon the fine adjustment, 
turning it back and forth so as to observe now the top and now the 
deeper portions of the specimen, for it is magnified in depth as well as 
in breadth. 

It is often very difficult to find a very small specimen with a high 
power lens, for the space in which it lies is magnified to several feet in 
diameter. A good plan is to use a low power lens for finding the speci- 
men, and then after bringing it to the center of the field, to substitute 
the high power lens. 



LIVING BODIES AND CELLS 1 9 

Every movement of the specimen is magnitied as much as the speci- 
men itself. So great gentleness is needed in moving it under the ob- 
jective or else it will be moved out of view altogether. The microscope 
appears to reverse the sides of the specimen, so in order to move the 
image in any direction the specimen must be moved in the opposite 
direction. Care should be taken not to press the lens upon the speci- 
men. If the lens becomes dirty or moist it should be gently wiped 
with a soft, clean handkerchief. A little alcohol rubbed on will aid in 
removing the dirt. 

17. Preparation of specimens. — Specimens are examined 

upon glass plates, called slides. The regulation size is 
three inches long and one inch broad. Specimens must 
be very thin, so as to show only a single layer of cells or 
fibers. A liquid specimen should be a small drop; a powder 
should be only a tiny speck. A solid specimen is prepared 
in either of two ways. Its cells and fibers may be picked 
apart by means of two needles ; but this destroys the 
natural arrangement of the parts. So the method of 
slicing off extremely thin layers with a sharp razor is 
more often used. This requires special training. Nearly 
all specimens should be examined in a liquid. Water will 
do for nearly all. Glycerine may be used if the specimen 
is to be kept, for it does not evaporate. A drop is placed 
over the specimen on the slide. Over the drop of liquid 
it is well to place a thin piece of glass, called a cover glass ^ 
for the purpose of protecting the objective from the 
liquid, and the specimen from currents of air. Air bub- 
bles under the cover glass interfere with the view. They 
can be forced out by gently pressing upon the cover glass ; 
but with care the cover glass can be applied so as to avoid 
them. A supply of slides and cover glasses is a necessary 
part of every microscopic outfit. 

A few fibers scraped off from a handkerchief or a few 
scales from the back of the hand are good specimens for 



20 APPLIED PHYSIOLOGY 

practice. A tiny bit should be placed upon a slide and a 
drop of water placed upon it, and the whole covered with 
a cover glass. Begin to examine it with the lowest powers 
of the microscope, and so gradually learn to use the higher 
powers. 

SUMMARY 

1. Physiology tells how living beings eat and grow and act. 

2. The ameba is a tiny lump of living jelly, which eats, 

and moves, and produces young amebas. 

3. The body of a man is made of tiny cells like an army 

of amebas. 

4. Each cell is a lump of thick jelly, in which a small 

mass called the nucleus may usually be distin- 
guished. The cells are held in place by strings 
called connective tissue. 

5. Each cell moves, eats, and grows, and produces other 

cells like the first. 

6. The mind lives in the body formed by the cells. 

7. The cells obey the mind. When the mind loses con- 

trol of them the body is dead. 

8. Each cell does some special kind of work for the 

benefit of the rest. 

9. A collection of cells doing a special kind of work is 

called a tissue. 

10. A collection of different tissues always arranged in a 

definite and compact shape is called an orga7i. 

11. A definite series of tissues and organs scattered 

through the body for a definite purpose forms a 
system. 

DEMONSTRATIONS 

I. Scrape the inside of the cheek with a sharp knife and examine 
a drop under the microscope, with a power of at least 100 diameters. 



LIVING BODIES AND CELLS 21 

Notice the flat scales of irregular shape. Each scale is a separate 
living cell. It is nearly transparent, but its nucleus appears as a 
slightly darker spot. Make a drawing of the cells. 

Examine cells scraped from the skin upon the back of the hand ; 
and cells scraped from the pulp of a leaf. Examine a bit of the green 
scum, called pond alga, which forms upon stones in fresh-water ponds. 
Notice the long cells joined end to end and containing green matter. 

2. Take a drop of stagnant slimy water from a rain barrel or from a 
kitchen drain or from a stagnant pool. Examine it with a power of at 
least I GO diameters. A specimen of the ameba is likely to be found 
rolling about. Notice its nucleus, and also dark spots in its body which 
are probably food which it has swallowed. Make a sketch of an ameba. 



REVIEW TOPICS 

1. Define Anatomy. 

2. Define PJiysiology. 

3. Define Hygiene. 

4. Describe an ameba. 

5. Describe a cell. 

6. Describe connective tissue. 

7. Give the three tests by which a cell or other body is 

known to be alive. 

8. Give other distinctions between living and lifeless 

bodies. 

9. Give the relation of the mind to the cells of the body. 

10. Define a tissue and name the different tissues of the 

body. 

1 1. Show that the blood is a tissue. 

12. Give the different 7?// zV/i" in the body. 

13. Define an organ. 

14. Define a system. 

15. Describe the instrument by means of which the dif- 

ferent cells and tissues of the body are studied. 



CHAPTER II 
ELEMENTS OF THE BODY 

18. Proximate principles. — The cells of all animals con- 
tain the same substances, differing in amount and arrange- 
ment, yet alike in composition. The simple substances of 
which the cells are composed are cdM^di pjvxhnate principles . 
The most important proximate principles are water, albu- 
min, fat, sugar, salt, lime, soda, and potash. 

19. Water and solution. — Water forms nearly three 
fourths of the weight of the body and is present in every 
part. It reaches each minute part of the body through 
the firm walls of the organs. Water has the power of 
dissolving solid substances, so that they retain all their 
properties unchanged. Sugar in water is sugar still; in 
fact, we can appreciate what sugar is only when it is dis- 
solved. When a substance is dissolved in a liquid, so that 
each remains unchanged in its essential properties, the 
result is a solution. Most solutions will go anywhere 
water itself will go. In the stomach the food becomes 
dissolved, and is taken into the blood tubes. The blood 
contains a solution of food which penetrates into the spaces 
around each cell, carrying nourishment to the cell and 
washing away its waste matters. Water makes the tissues 
limber and slippery, so that they bend and move easily. 
By means of the perspiration which carries off surplus heat, 
water regulates the heat of the body. About three quarts 
of water are taken into the body each day. 



ELEMENTS OF THE BODY 23 

Water is composed of two gases, hydrogen and oxygen, 
very firmly united. 

20. Albumin. — The protoplasm of the living cells of the 
body is almost entirely composed of a substance like the 
white of an egg. Because it turns white when heated, it 
is called albumin (from the Latin albus, white). Pure 
albumin is hard and brittle as the white of an egg is when 
it is dry. In the body it is dissolved in from five to twenty 
times its own weight of water. This solution in water is 
what is meant by the albumin of the body. In the blood 
it is liquid, in the flesh it is somewhat jellylike, and in 
the skin it is strong and tough. It is a very complex 
body which only plants can form. Animals rhust get it 
from vegetables and change it into their own bodies. 
When once formed it may become part of the bodies 
of several successive animals, as one makes food of 
another. - 

Albumin forms the principal part of the protoplasm of 
all living cells. Some is used in performing the work of 
the body and does not reach the cells. About four and 
one half ounces of pure albumin must be eaten each day 
to supply the needs of the body. 

21. Forms of albumin. — There are many forms of albumin, all 
having essentially the same properties. The white of eggs is almost 
pure albumin. Lean meat is composed mostly of another form ; cheese, 
gelatine, and glue are composed mainly of still other forms. 

22. Coagulation. — Most forms of albumin may be hard- 
ened either by heat or acids, and once hardened they can- 
not be dissolved again to their original state. A boiled 
egg illustrates this hardening. Changing a Hquid to a 
jellylike or solid form so that it cannot be changed back 
to its original form is coagulation. Coagulation of its 
albumin destroys the life of a cell. 



24 



APPLIED PHYSIOLOGY 




23. Putrefaction. — When albumin is kept moist and exposed to 
the warm air it decays or putrefies, becoming soft and finally completely 
dissolving, and at the same time giving off offensive odors. If the 
albumin is kept dry it shrivels up and finally crumbles to an odorless 
powder. Pure sugar or fat will not putrefy, although both may become 
sour, but both often contain a slight amount of albumin, and this may 
putrefy, giving them a slight taste and odor. 

24. Diffusion. — When salt and water are placed in a 
bag of thin skin and suspended in a dish of water, some 

of the salt and water will pass through 
the walls of the bag and will mingle 
with the water in the dish, and, on the 
other hand, some water will pass into 
the bag. This will go on until the 
water in the dish is of the same salt- 
ness as the water in the bag. The act 
of passing through a membrane appar- 
Diffusion at the begin- ently impervious is a form of diffusion. 
ning of the process. Without pressure albumin will not dif- 
fuse except in the form, cdW^A peptojte, 
which is produced from the others by 
digestion. Peptone readily diffuses 
through the thin sides of the blood 
tubes in the walls of the intestine, and 
so reaches the blood. 

25. Iron-bearing albumin. — The nu- 

_.„ . cleus of vegetable cells is composed of a form of 

Diffusion at the end „ . ,, , , „ . , . , 

of the process. albumm called nucleo-albwmn, which contams 

iron. There are from thirty to sixty grains of 

iron in the human body, all of which is united with the albumin, so 

that the metallic properties of the iron are completely absent. A 

small amount of this iron-bearing albumin is found in the nucleus of 

every cell, both vegetable and animal, and seems to be essential to the 

growth and division of the cell. In an animal this substance gives 

origin to the substance called hemoglobin, which foriiis the coloring 




ELEMENTS OF THE BODY 25 

matter of the red blood cells. The iron gives it the power to carry 
oxygen from the lungs to all parts of the body. Only one or two 
grains of iron are required each day to supply the loss of the iron in 
the body, and several times that amount is eaten daily in our food. 

26. Fats and oils. — Fats are a series of smooth, slip- 
pery substances found in all animals, and in most vege- 
tables. About five per cent of the human body is fat. It 
is scattered between the cells of all parts of the body, but 
in places, as in the walls of .the abdomen, it forms thick 
layers. All fats become 
liquid when heated, but 
those that are liquid at 
ordinary temperatures are 
called oils. In the living 
body fat is always in a 
liquid state, stored in 
thin-walled pockets made 
of connective tissue. By 
boiling, the pockets are Fat tissue (x 100). 

softened and the fat runs Connective tissue cells form pockets in which 

the hquid fat is stored, 

out upon the water. Each 

pocket is from ^ Jq^ to ^-^-^ of an inch in diameter. The fat 
is produced from the albumin of the cells by a breaking- 
down process. Fat is a simple substance compared with 
the complex albumin. Probably all the fat which is stored 
in the body is made out of albumin. 

27. Emulsion of fat. — However much fat may be shaken with 
water it will remain in tiny particles which soon rise to the surface. If 
a little white of ^g% is added, the fat will divide into finer particles and 
will remain in the water much longer. A mixture of fat and water is an 
etnulsion. No emulsion is permanent, but the fat will rise to the surface 
in time. Milk is the most perfect emulsion, but even in milk the cream, 
or fat, rises in a few hours. 




26 



APPLIED PHYSIOLOGY 



28. Saponification of fats. — When fat is boiled with soda or 
potash it is broken up into a small amount of glycerine and a large 
amount of a substance called a fatty acid. The fatty acid unites with 
the soda or potash to form soap. When by any means fat is broken 
up with soda or potash, forming soap, the process is called saponifica- 
tio7t. Both soaps and emulsions are continually being formed during 
the digestion of fat. 

29. Use of fat. — The fat of the body is a living garment, 
retaining heat and protecting the body from the cold, and 
rounding out the rugged outlines of the bones and muscles. 
It is a cushion, protecting the internal organs from injury. 
It is also a store of food to be used in sickness when food 
cannot be eaten. The fat which is eaten is used up in 
warming the body. Thus fat acts as a food, as armor for 
the body, and as useful and ornamental clothing. About 
three ounces of fat must be eaten each day. 

30. Starch and sugar. — Starch is produced almost en- 
tirely by plants and is stored in the form of little grains 

which will not dis- 
solve in cold water. 
Grains of potato starch 
appear like oyster 
shells and show dis- 
tinct markings as 
though they were built 
up in layers. It is 
supposed that starch 
grains grow by deposits 
of successive layers of starch between which are layers of 
a waterproof substance called cellulose or plant connective 
tissue. When the grains are boiled, they swell and burst 
and then dissolve, forming a paste. As a plant grows, it 
uses the starch in building up sugar, wood, cotton, cellu- 
lose, and other plant substances. Starch, sugar, wood, cot- 




starch Grains ( X 400) . 

, of potato. b, of corn. 



ELEMENTS OF THE BODY 



2; 




-^^Bif 



A thin slice of potato ( x 200) . 

a Albuminous and fibrous pockets. 
b Starch grains in the pockets. 



con, and cellulose are similar in chemical composition, but 
differ widely in character. 

Wood is of no use to 
the body, but starch and 
sugar are common foods. 
Starch is changed to 
sugar before it becomes 
a part of the body of 
man. Only a little sugar 
is found in the body at 
one time, for almost as 
fast as it enters it is 
used up to produce 
warmth. About five 
ounces of starch or sugar 
must be eaten each day. 

Minerals. — The minerals salt, hme, soda, and potash, 
are always found in the body. 

31. Salt. — Common salt is found in the bodies of all 
animals, and a less amount in vegetables also. There are 
about six or seven ounces of salt in the human body. In 
animal food there is enough salt to supply the needs of 
the body, but some must be added to vegetable food. So 
flesh-eating animals, like dogs and cats, will not eat salt, 
while vegetable-feeding animals, as horses, like it. 

Salt gives an agreeable taste to food, and this causes the •' mouth to 
water," and all the other digestive fluids to flow freely, so that the salted 
food is quickly and easily digested. 

Some kinds of albumin in the body will dissolve in water only when 
salt is present, and if it is diminished in amount, or is absent, these 
albumins cannot do their work. 

Salt diffuses very readily, and also aids in the diffusion of all kinds 
of food So salt has very important uses in the hody. and when it is not 
used there is great suff'ering. The proper amount of salt is present in 



28 APPLIED PHYSIOLOGY 

the food when food tastes just agreeably salt. About one half an ounce 
needs to be eaten each day. 

32. Lime. — A small amount of lime is found every- 
where in the body, but bone is over one half lime. In all, 
there are between ten and twelve pounds of lime in the 
body, but only six grains need be eaten each day. Much 
more than this amount is found in all common food. The 
main use of lime is to give stiffness to the bones. It is 
mixed with the cells and fibers of the bone, just as starch 
is mixed with the fibers of linen to make it stiff. 

33. The alkalies — soda and potash. — Some substances 
are sour and burning to the taste, and can corrode or eat 
away flesh and metals. When soda or potash is mixed 
with such a substance, both ingredients in the mixture are 
changed and a new substance unlike either is formed. 
For instance, strong vinegar is such a sour, corrosive sub- 
stance. When soda is added to it the mixture bubbles for 
a time, and then the liquid is no longer sour or irritating, 
but has a flat, bitter taste, and both the soda and vinegar 
have become changed. A substance which is sour to the 
taste and corrodes metals and flesh, and unites with soda 
or potash with a bubbling, is called an acid. Soda and 
potash are called alkalies. They also can corrode certain 
substances, but they always unite with acids at the first 
opportunity, and by their union each is changed to a 
less harmful form. So alkalies destroy or neutralize 
acids, and acids neutralize alkalies. 

34. Chemical action. — When two substances are mixed 
together so that each becomes changed and substances 
unlike either are produced, the process is called chemical 
action. Sugar will dissolve in vinegar, but it still remains 
sugar, and so the mixture is called a solution (see p. 22). 
In contrast with it, when soda is dissolved in vinegar it is 



ELEMENTS OF THE BODY 29 

completely changed, and so forms an example of cJicniical 
action. Some substances are very prone to mix to form 
solutions. Thus, impure salt has such an attraction for 
water that it takes it from the air and becomes damp. So 
salt is said to have an affinity for water. In the same 
way some substances are very prone to mix so as to be- 
come changed by chemical action. Thus, there is always 
chemical action between soda and vinegar when they are 
brought together, so soda is said to have a chemical 
affinity for vinegar. In the same way, air has a great 
''chemical affinity" for zuood in a fire. The chief value of 
gold comes from the fact that it has no chemical affinity at 
all except for one or two uncommon substances. So it 
will remain unaltered in the midst of substances which 
would destroy other metals. 

35. Use of alkalies. — If a fluid contains an acid, it is 
said to be acidm reaction ; if an alkali it is alkaline ; and if 
it contains neither it is neutral in reaction. Now, the blood 
is always alkaline from the presence of a small amount of 
soda and potash. Acid products are being formed in the 
body continually, and the duty of the alkalies is to unite 
with them at once and change them to harmless sub- 
stances, which may be handled by the blood in safety. 
The alkalies are found in nearly all foods. 

36. Chemical actions in the body. — Eveiything ^vhich makes 
up the cells and fluids of the body is composed of some or all the sub- 
stances — water, albumin, fat, sugar, or starch, with the minerals — 
salt, lime, and soda and potash. These must be eaten to sustain life, 
and so they are foods. Other kinds of substances are harmful or 
poisonous. All food substances are eaten three times a day, and yet 
only water and the minerals leave the body in anything like the form 
in which they entered. The rest are entirely changed by chemical 
actions and leave the body as gases or liquids or as solids dissolved in 
water. The disrestion of food from the time it is taken into the mouth 



30 APPLIED PHYSIOLOGY 

is a chemical action, as is also its becoming a part of the living cells. 
Breathing and the production of the waste matters of the body are 
also chemical processes. 

These chemical processes can be followed and even imitated in a 
laboratory. The living principle in the body directs the work, but 
uses few processes which are not also used outside of the body. It has 
been a great triumph for science to liberate men from the superstition 
that the chemical and physical laws of our bodies were governed by the 
arbitrary feelings of indwelling spirits, and so were different from the 
laws governing lifeless creatures. 

SUMMARY 

1. The cells of the body are composed of five substances, 

viz., water, albumin, fat, sugar, and minerals. 

2. Water is three fourths of the body. It carries food to 

the cells and washes away their waste matters. 

3. Albumin is like the white of eggs. It forms the pro- 

toplasm of all cells. It warms the body, and gives 
it strength and weight. 

4. Fat is in pockets between the cells. It protects and 

heats the body. 

5. Starch and sugar are similar substances. They warm 

the body. 

6. The minerals in the body are salt, lime, soda, and 

potash. They are found in all food. In addition 
some salt must be eaten. 

7. Salt aids in the preparation and distribution of food to 

the cells of the body, 

8. Lime stiffens the bones. 

9. Soda and potash destroy irritating acids within the 

body. 

10. Water, albumin, sugar or starch, fat and minerals, are 

foods and must be eaten to sustain life. 

11. Most of the vital actions of the body can be imitated 

in a chemical laboratory. 



ELEMENTS OF THE BODY 3 1 

DEMONSTRATIONS 

3. Illustrate the properties of -albumin by the \vhite of an egg. 
Notice its sticky character. Dry some upon a piece of paper over a 
fire and notice ili brittle, gluelike character, and that it will again dis- 
solve in water. Boil some and notice that it becomes hard and will 
not redissolve. Set some iside and notice that it decays. 

4. Inclose a lump of wet flour in a muslin bag and wash it until the 
water is clear. This removes the starch grains and leaves the grain 
albumin or gluteti pure. Notice its tough and sticky character. 

5. Show samples of olive oil, lard, and tallow. Show that lard 
melts at about the temperature of the body, and so is fluid in the body. 

6. Shake together some oil and water. Notice that the oil at once 
floats upon the surface. Now shake the oil ./ith 3ome lime water, and 
notice that it no longer floats, but that the mixture looks milky, while a 
few very small oil drops can be seen floating in the liquid. Explain 
that this is an ejnulsion. 

7. Stir together some castor oil and caustic soda, gently heating the 
mixture, and notice that it forms soap. 

8. Scrape a potato into a basin of water. Wash it about and notice 
that the shreds of potato will float, while a white substance will settle 
to the bottom of the basin. Explain that this substance is starchy and 
that our great-grandmothers used this method to make starch for 
laundering. 

9. Place a small drop of the wet potato starch upon a glass slide 
and examine it with a power of at least 50 diameters. Notice that the 
starch grains appear like oyster shells. Examine also some corn starch 
and notice that each grain looks like an irregular cube with a star-shaped 
center. Sketch the starch grains. 

10. Boil some starch and notice that it swells and forms a jellylike 
paste. 

Iodine turns starch blue. Apply a drop of the tincture of iodine to 
the starch and notice the blue color. Apply it to bread, cake, flour, 
etc. Notice the blue color, showing that they all contain starch. 
Notice that meat does not respond to the test. 

11. Show specimens of sugar. Brown sugar is the impure form, 
while granulated sugar is the pure crystallized form. Show some sugar 
scraped from the outside of raisins and explain that this is glucose or 
grape sugar, and that all sugar and starch must be changed into this 
form before it can be used by the body. 



32 APPLIED PHYSIOLOGY 

12. Burn some bread or meat and save the ashes. The ashes 
represent the mineral part of food, and consist mainly of lime, salt, 
soda, potash, and iron. 

13. Show diffusion by tying a piece of parchment over the end of a 
large glass tube. Fill the tube with salt and water and immerse it in 
ajar of fresh water. In a little while the liquid will rise in the tube, 
while the water in the jar will begin to taste salt. The process will 
continue until the water in the tube and in the jar are of equal saltness. 
If the water in the jar were renewed, all the salt could be extracted 
from the tube. 

14. Show the affinity between acids and alkalies by dropping soda 
in vinegar. Notice that the mixture boils and foams, and both sub- 
stances become changed. Drop some soda in water and it simply 
dissolves and forms a solution. 

15. Drop a pinch of baking soda in a small cup of water. Then 
stir in some dilute hydrochloric acid, drop by drop, until the mixture 
ceases to bubble. Taste the mixture and notice that it is salt. Ex- 
plain that the hydrochloric acid and the soda have formed a chemical 
combination and each has neutralized the other. The new substance 
formed is chloride of sodiicm or common salt. 

REVIEW TOPICS 

1. Define and name \k\Q, proximate principles, 

2. Describe water and define a solution. 

3. Describe albtimijt. 

4. Describe diffusion. 

5. Y)Q?,cr\b& putrefaction. 

6. Describe micleo-albiimin, and its relation to iron, 

7. Describe /^/i- and oils. 

8. Describe an emulsion. 

9. Describe saponification. 

10. Describe starch, sugar, and wood. 

1 1 . Describe salt. 

12. Describe lime. 

13. Describe the <2/^^/2>j-. 

14. Define chemical action and chemical affinity. 

15. Name some chemical actions in the body. 



CHAPTER III 



OXIDATION 







OxY^en imlggif. 



37. The nature of burning or oxidation. — In addition to 
the substances taken in as food, the body is continually 
taking in oxygen by the breath. The air which is 
breathed is four fifths nitrogen gas and one fifth 
oxygen gas. When air is fed to fuel in the hot 
fire box of a boiler, burning takes place. Burn- 
ing is a chemical process. Oxygen unites with 
the carbon and the hydro- 
gen of the wood, so that 
both the wood and the 
oxygen disappear. The 
carbon and part of the 
oxygen form carbonic acid 
gas. The hydrogen and 
the rest of the oxygen 
form water. Both sub- 
stances pass off in the smoke. What is left as ashes is 
the mineral part of the wood. 

By the burning, heat and a flame are produced. The 
heat can be used to make steam which will drive an 
engine and do work. Burning is called oxidation. 

38. Oxidation within the body. — The body also is an 
engine, — self-regulating and self-sustaining. The oxygen 
which is breathed into the body slowly burns food and 
the cells, just as it oxidizes the wood under the boiler of an 

OV. PHYSIOL. — 3 33 



3Z 



^ 



Diagram of burning or oxidation in a 
stove. 



34 APPLIED PHYSIOLOGY 

engine. The process goes on so slowly that no flame 
is produced, but the same amount of heat is produced as 
though the same substances were burned in a furnace. 
Some of this heat is used to warm the body, and some 
is changed to power which enables the body to do work, 
either of motion, or of manufacturing the various products 
of the body or of thought. Oxidation is an essential 
process of life ; when it ceases for an instant life ends. 
When the air is cut off from the body for only a minute, 
a great feeling of suffocation comes on, and within two 
or three minutes the body dies. 

Oxidation goes on in each cell, but especially in the 
cells of the lungs and liver. It is a process of life, and 
in a living cell it can be hastened or retarded according 
to the needs of the body. 

By the oxidation within the cells of the body, carbonic 
acid gas, water, and ashes are formed, as in a furnace. 

39. Oxidation of albumin. — An ounce of albumin is 
completely oxidized by an ounce and a half of oxygen. 
The ashes which are produced are partly the sulphur of 
the albumin and partly the nitrogen, which holds some 
of the carbon, hydrogen and oxygen, combined in a 
solid called urea. Urea must be given off by the kid- 
neys and skin as fast as it is formed. When there is 
not enough oxygen to burn the albumin entirely, other 
substances resembling urea are formed, just as a stove 
smokes instead of burning brightly when the draft is 
closed. Some of these substances are very poisonous. 
The albumin of the living cells must be oxidized and 
replaced continually. Much of the albumin of the food 
is oxidized before it reaches the cells. 

40. Oxidation of fat. — An ounce of fat is completely 
oxidized by three ounces of oxygen. So it will produce 



OXIDATION 



35 



twice as much heat as the same amount of albumin, and 
is thus a good food for cold weather. It leaves no ashes 
behind, for it contains no mineral matter. 

41. Oxidation of sugar. — An ounce of sugar is com- 
pletely oxidized by one and one fifth ounces of oxygen. 
So it produces only about half as much heat as fat. It 
is much more easily oxidized than fat or albumin. When 
the three substances are mixed together as they are in the 
body, the oxygen will go to the sugar in preference to 
the fat or albumin, and the latter two substances being 
unburned will accumulate in the body. Thus sugar is 
said to be fattening. The water and the minerals of the 
body cannot be oxidized, but enter 
and leave the body unchanged. 

42. Reconstruction of living mate- 
rial by plants. — In every animal the 
living cells are continually uniting 
with the oxygen of the air and giving 
out carbonic acid gas, water, and min- 
eral matters. From these waste mat- 
ters plants reconstruct the substances 
which were oxidized in the body. 
The first substance produced seems 
to be starch, and from it as a basis all 
other parts of the plant and of ani- 
mals are built up. 

The plant cells which contain \^ 
green coloring matter called chloro- 
phyll, are set apart for the special 
work of reconstructing starch from 
oxidized material. To them the sap 
brings water from the soil, and carbonic acid gas from 
the air. In the chlorophyll these substances are recon- 




Chlorophyll in pond algae. 

a Chlorophyll arranged in 

a spiral. 
b The clear bodv of the cell. 



36 



APPLIED PHYSIOLOGY 



structed into starch. Using 
construct fat and albumin and 



starch as a basis, plants 
all other substances found 
in the plant. 

43. The sun's work 
in reconstructing living 
material. — When oxygen 
unites with the carbon and 
hydrogen of the burning sub- 
stances, heat and energy are 
given out. Just as much 
heat and force must be used 
in tearing away the oxygen 
as was given out during the 
oxidation. The sun furnishes 
this heat and force. The 
chlorophyll acting as the ma- 
chine and using the sun's rays 
for power, frees most of the 
oxygen from the carbonic 
acid gas and water, and gives 
it back to the air. At the 
same time it unites the re- 
maining oxygen with the car- 
bon and hydrogen to form living starch. Thus the real work of con- 
struction is done by the sun. When the starch is oxidized, oxygen goes 
back to the hydrogen and carbon, and the same 
amount of heat is given off as was taken from 
the sun when starch was formed. 

The heat of oxidation can be traced back to the 
sun's heat stored up by living beings or beings 
once alive. All the carbon of a tree is the car- 
bonic acid gas of the air with its oxygen taken 
away by the sun's force acting through chloro- 
phyll. Coal is the carbon of trees changed in ^, , ,, 
^ -^ - . r^ • , Diagram of the stream 
form durmg ages of burial. of material flowing through 

man. 

44. Conservation of energy. — The 

energy of the sims heat expended upon the plants in 




Diagram of the restoration of oxygen to 
the air after oxidation, and of the rebuilding 
of burned material into living forms. 




OXIDATION 37 

bygone ages was conserved in the coal, and now can be 
made to appear again 3.s force in a steam engine. This 
force may run an electric dynamo, and the electricity can 
be transported silently over miles of wire, to appear as light 
rivaling its original source, the sun. Through all its 
changes the original energy is preserved. 

Observation of the three facts, (i) the heat of the sun 
acting through plants to tear the oxygen from the carbon 
and hydrogen, (2) the reunion of the substances in oxi- 
dation with the development of the original heat of the 
sun, and (3) the various forms of power into which the 
energy can be changed, has given rise to the principle that 
any fonn of energy can be cJianged into aiiother form ivitJioiit 
loss. This principle is called the conservation of energy. 

This principle is exemplified in the human body. The 
energy for the work done by the body is the heat derived 
from the oxidation of its food. 

45. Relation of plants to animals. — The oxygen of the 
air would all be used up in a few years if it were not continually torn 
away by plants from its combinations in carbonic acid gas and water. 
The carbon and hydrogen would also disappear ; but the sun and 
chlorophyll continually renew the supply both of food and of oxygen. 
Thus there is a stream of material flowing from lifeless soil and air. It 
becomes alive in the plant and again in the animal, and then is suddenly 
oxidized to a hfeless form, and given back to the soil and air, only to 
repeat the round of life. Plants build up living material which animals 
use as food and then oxidize back to the form in which it existed before 
the plant touched it. Plants give off oxygen which supports animal 
life. Each lives upon what the other discards. 

46. Organic substances. — ^ Substances which are built 
up by living beings are called organic. Thus the plant 
takes carbon from the carbonic acid gas in the air, and 
builds it up into an organic substance, which forms part of 
the plant. 



38 APPLIED PHYSIOLOGY 

47. Difference between plants and animals. — (i) The 

ability to live upon the ordinary waste products of animal life, or, in other 
words, to reconstruct organic matter out of crude minerals and gases ^ is 
a distinguishing mark of a plant. On the other hand an animal always 
requires orgajiic food, and cannot live upon the soil and air. Yet the 
lowest animals very closely resemble plants, and owing to the difficulty 
of ascertaining the true source of their food the position of some living 
bodies is still a matter of dispute. 

(2) In animals the cells are bound together by strings of connective 
tissue, which is an albuminous substance of soft consistency. In plants 
the substance between the cells has the composition of starch (see 
p. 27). It is a hard and firm substance, and gives the rigid strength to 
the plant or tree. The outsides of the plant cells often have a thick 
coating of the same substance. When it is deposited in so great an 
amount as almost to replace the cells the substance forms wood. Yet 
in some plants it is entirely absent, so that the distinction applies only 
to higher forms of life, where other distinctions between plants and 
animals are more obvious. 

(3) Most animals have the power of voluntary motion, while most 
plants are fixed to one spot. Yet some animals, as the coral, have no 
more motion than a flower which opens and closes during the day. On 
the other hand some water plants are continually moving about by 
means of vibrating hairs projecting from their bodies. 

Some plants also move if irritated. The plant called Venus's flytrap 
has stiff, toothed leaves, hinged together in twos so as to open and shut 
like a rat trap. When a fly alights upon the open leaf it suddenly closes 
upon the insect, crushing it to death. This plant exhibits more move- 
ment responsive to a slight irritation and directed to a distinct purpose 
than many true animals. 

(4) Most animals have a digestive ttibe, while plants have no organs 
of digestion, unless the leaves can be called such. Yet in some animals, 
as the ameba, the body looks nearly the same throughout. 

(5) Most plants 2X^ green in color, from the presence of chlorophyll. 
Yet many plants, as toadstools, are destitute of chlorophyll. 

48. Source of life. — In the oxidation and reconstruction 
of animals and plants no new life is created. Lifeless 
material is endowed with Hfe by material already living, 
and in its turn the new material imparts life. The same 



OXIDATION 39 

life continues through all the changes of the body, 
although not a single particle of the original body may 
remain. The body is but the house in which life resides. 
The original source of life itself has never been found. 
The Bible gives the only known origin of life : 

*'And God said, Let the earth bring forth grass, the 
herb yielding seed, and the fruit tree yielding fruit after 
his kind, whose seed is in itself, upon the earth : and it 
was so. 

*' And the earth brought forth grass, and herb yielding 
seed after his kind, and the tree yielding fruit, whose 
seed was in itself, after his kind : and God saw that it was 
good." — Gen. i : 11-12. 



SUMMARY 

1. Oxygen unites with carbon and hydrogen, and pro- 

duces heat. The process is called biiniing or oxida- 
tion. A steam engine transforms heat into work. 

2. Oxygen from the air is continually entering the body. 

3. Within the body it is continually uniting with the 

albumin, fat, and sugar, and producing heat, some of 
which is transformed into work. This is the essential 
process of life. 

4. By oxidation, the albumin, fat, and sugar become car- 

bonic acid gas, water, and urea, and are given off 
from the body. 

5. The green coloring matter of plants forms the machine, 

by means of which the sun's heat tears the oxygen 
away from the carbonic acid gas and water and 
forms organic substances again. 

6. Plants prepare food for animals, and animals prepare 

food for plants. 



40 APPLIED PHYSIOLOGY 

7. All through the oxidation and reconstruction of the 

body life remains the same, and no new life is 
created. 

8. The Bible gives the only known explanation of the 

origin of life. 

DEMONSTRATIONS 

16. Lower a lighted candle into a wide-mouthed bottle. When it 
goes out pour in a little lime water, then stop the mouth of the bottle 
and shake it. The water becomes milky, showing that carbonic acid 
gas has been produced. By means of a straw or glass tube blow a 
little air through a cup of lime water and notice that again the water 
becomes milky. This shows the carbonic acid of the breath. 

17. Hold a lighted match under a cold tumbler. In a few seconds 
drops of moisture will condense upon the inside of the glass. Explain 
that the water is formed by the union of the hydrogen of the match 
stick with the oxygen of the air. 



REVIEW TOPICS 

1. Describe oxidation and its products. 

2. Show how oxidation takes place in the body. 

3. Describe the oxidation of each proximate principle. 

4. Describe the series of changes by which the oxidized 

materials of the body are again built up into living 
bodies. 

5. Define and illustrate conservation of e^iergy, and apply 

it to man's body. 

6. Define organic bodies. 

7. Give points of difference between plants and animals. 

8. Give the only known source of life. 



CHAPTER IV 



FERMENTATION AND ALCOHOL 



49. Production of alcohol and vinegar. — Unless great 
care is taken to preserve it, a weak solution of sugar soon 
turns to vinegar ; a stronger solution 
turns to alcoJiol, while a thick, sirupy 
solution remains unchanged. Every- 
where there are scattered minute living 
germs which, falling into a moderately 
strong solution of sugar in water, grow 
and produce oval plants each about 
^Q^QQ inch in length. A collection of 
these plants is called yeast. By their 
growth and multiplication they change 
sugar to alcohol and carbonic acid gas. 
The gas bubbles up through the 
liquid and makes a froth upon the top, 
while the alcohol remains in the water. 
If only a small quantity of sugar is present another kind 
of germ from the air enters and grows, becoming tiny 




Yeast plant cells (x 500), 



rodlike plants, each about y-o^o-o ^^^^ ^^ length. By 
their growth and multiplication they change the alcohol 
to vinegar. They collect in a mass called the mother of 



Boiling destroys both the yeast and vinegar germs. If 
the sugar and water are boiled and at once sealed tightly, 
so that new germs cannot enter, the solution will keep 

41 



42 APPLIED PHYSIOLOGY 

for an indefinite time. Fruit when boiled and at once 
sealed in air-tight cans will keep unchanged for a long 
time. If there is a great deal of sugar present no germs 
at all will grow, and the solution will keep indefinitely. 
This is why fruit can be preserved in open jars if a great 
deal of sugar is used. 

50. Fermentation. — Changing sugar to alcohol or vine- 
gar is an example of fermentation, A substance which 
can change the composition of other bodies without losing 
its own identity or characteristics is a ferment. A very 
small amount of a ferment can change a very large amount 
of another substance. 

A very small amount of yeast will cause an indefinite 
amount of sugar to become changed to alcohol or vinegar. 
At the same time the yeast may not grow weaker, but 
on the contrary may become stronger than at first. In the 
same way a small amount of " mother " will change a 
large amount of weak alcohol to vinegar, and itself will 
greatly increase in amount. 

51. Kinds of ferments. — Nature uses many ferments in her 
actions. Some are living beings and some are lifeless substances. The 
chief part of the digestion of food is done by lifeless ferments. Fer- 
mentation is commonly spoken of as a process of decay, but the 
common process of decay or rot is in itself only a special kind of fer- 
mentation. Ordinary decay is caused by a living being like the 
vinegar germ. By its growth and multiplication it softens and liquefies 
the albumin of animal and vegetable matter. This process is called 
putrefaction (see p. 24) . Some of the matter passes off as foul smell- 
ing gases, while the liquid part soaks into the soil. Putrefaction is 
nature's way of giving dead bodies back to the soil and air so that 
plants can build them into useful forms again. 

Yeast germs are found everywhere, but they are often grown in wet 
meal or flour. The mass is then dried in cakes and sold as yeast. 
When a small piece is added to sugar and water it starts alcoholic fer- 
mentation at once. Alcoholic fermentation only is usually meant when 



FERMENTATION AND ALCOHOL 43 

the term fcrmetitafiofi is used alone. An adjective signifying the 
special form of fermentation is used to indicate any other form than 
the alcoholic. Thus there is acetous or vinegar fermentation, and 
putrefactive fermentation. 

52. Bread making. — By the growth of yeast plants in 
bread dough some of the sugar in the flour is changed 
to carbonic acid gas and alcohol. The gas bubbles up 
through the dough, making it porous and light. When 
the bread is baked, alcohol is driven off and the yeast 
germs are killed by the heat. They are eaten with the 
bread, for they are perfectly wholesome. When germs 
of vinegar or other acid fermentations enter the bread 
and grow, the bread sours. These germs grow more 
slowly than yeast, and usually do not have time to de- 
velop. But if the bread is a long time in rising, they 
may grow and make the bread sour. 

53. Fermented drinks. — Man uses the same process to 
produce drinks, which are erroneously supposed by many to 
act as a beneficial food, quenching thirst and giving strength 
to the body and power and joy to the mind. There are 
three classes of such drinks, all containing alcohol as an 
essential part. 

54. Malt liquors. — The commonest form is what is 
known as fnalt liquors. Barley and other grain are mois- 
tened and permitted to sprout until the new stalk is about 
one half inch in length. This changes much of the starch 
of the grain to sugar. The sugar is dissolved out by boil- 
ing the grain along with hops and various other flavoring 
substances. Then yeast is added and alcoholic fermen- 
tation occurs. The result is beei\ It contains from one 
to ten per cent of alcohol. Much of the flavoring which 
is often added to it is not only injurious, but actually 
poisonous. 



44 APPLIED PHYSIOLOGY 

55. Wines. — The second class of alcoholic liquors is 
witie. The juice is squeezed from grapes, blackberries, or 
some other fruit rich in sugar. Germs of alcoholic fer- 
mentation from their skins and the air set up fermentation 
in the juice and produce wine. Certain localities and cellars 
contain special kinds of germs which produce a peculiar 
flavor in the wine fermenting in that locality. In this way 
different kinds of wine are produced. Wine contains from 
five to fourteen per cent of alcohol. Fourteen per cent of 
alcohol in the juice kills the germs and stops the fermenta- 
tion. So wine cannot contain more than that amount of 
alcohol unless more is added. 

56. Distilled liquors or spirits. — The third class of 
alcoholic drinks is spirits, or distilled liquors. Alcohol 
boils at a temperature of 170° F., while water boils at 
212° F. Thus when a wine, or beer, or any other alco- 
holic solution is heated its alcohol will be changed to 
steam very rapidly, while the water will evaporate slowly. 
Therefore the steam will contain a larger proportion' of 
alcohol than the original liquor. This fact is put to use in 
separating alcohol from the solution in which it was pro- 
duced. The steam is conducted through a coil of pipe 
kept cool by running water. Its temperature is lowered 
and it is changed back to a liquid form. This new liquid 
is whisky, or brandy, or other spirituous liquor, according 
to the substance used in its manufacture. The process 
of its manufacture is called distillation. Spirituous liquors 
are about one half alcohol. 

57. Description of alcohol. — If the process of distillation 
is repeated the alcohol which passes over is still freer from 
water, until after three or four distillations it is almost 
pure. It is then a clear, colorless liquid like water. It has 
a sharp, sweetish taste and a peculiar odor. It causes a 



FERMENTATION AND ALCOHOL 45 

severe smarting sensation when applied to a raw sore or to 
the eye or mouth. It is a valuable and useful article when 
rightly used in the manufactures and arts. But men have 
formed the bad habit of liking its taste and the feelings 
which it produces. They drink strong drink solely for 
the sake of the alcohol which it contains. The alcohol 
has an injurious effect upon every part of the body. 
These effects will be described in detail as each organ is 
studied. 

58. Kinds of alcohoL — Alcohol is the name for a series of sub- 
stances formed out of the same elements, but varying in composition, 
yet alike in essential properties. The simplest form is called methyl 
alcohol, or wood spirits, and is formed by distilling wood. It has an 
unpleasant odor and taste, but nearly the same properties as common 
alcohol. It is much used in manufacturing and in the arts, as a substi- 
tute for common alcohol, on account of its cheapness. 

The next form, called ethyl alcohol, is the common alcohol made 
from wine, beer, etc. 

The fifth in the series is called a?nyl alcohol or fitsel oil, from the 
German fusel, bad liquor. It has a bad odor and nauseous taste, and 
is far more poisonous than common alcohol. It is formed in con- 
siderable quantities when potatoes are fermented. ■ But if the whisky 
stands for some years, the fusel oil becomes changed to ordinary 
alcohol. 

59. What becomes of alcohol in the body. — When taken 
into the stomach, alcohol passes into the blood with great 
rapidity. The body has the power of rapidly disposing of 
it either by giving it off, or, more probably, by oxidizing it 
to carbonic acid and water, and thus destroying it. At 
any rate, little or no alcohol can be found in any part 
of the body or in its waste, no matter how much is taken. 
But its oxidation takes place in an irregular way which is 
injurious to the body. 



46 APPLIED PHYSIOLOGY 

60. Effects of alcohol. — (i) Prevents fermentation and 
decay. — While alcohol is the product of fermentation, it 
has the power to prevent fermentation. The germs pro- 
ducing alcohol will not grow when alcohol is present in the 
proportion of 14 per cent. Germs of decay will grow in a 
much larger percentage of alcohol, but no germs will grow 
in a solution of one half alcohol. This fact is put to use 
in preserving specimens of animals and vegetables in 
museums, by placing them in spirits or alcohol. Since 
decay is dependent upon germs, the alcohol, by preventing 
their growth, prevents decay. It can also prevent the 
digestive ferments from acting upon food. 

(2) Extracts water from tissues. — Water and alcohol 
mix very readily. An uncorked bottle of alcohol takes up 
water from the air, and so becomes weakened. When 
alcohol is in contact with a wet substance, it appropriates 
some of its water, and the substance then shrivels and 
becomes firmer. Strong whisky can produce the same 
result in the body to a limited extent. 

(3) Hardens tissues. — Alcohol also hardens many ani- 
mal and vegetable substances by extracting their water and 
by coagulating t\vQ.\Y albumin. In museums this fact is put 
to use in hardening soft and delicate specimens of animals 
and vegetables, so they may be preserved and examined 
safely. It is not probable that this action occurs in the 
body, for nature pours out an abundance of water to dilute 
the irritating alcohol. 

Within the body the effect of extracting water from the 
tissues and of hardening albumin is to produce a smarting 
sensation which shows that the organs are being injured. 
There would be no limit to this action and death would 
soon take place if nature did not provide means for a 
partial protection against the substance. When any part 



FERMENTATION AND AECOHOL ' 47 

of the body is harmed, nature pours an abundance of 
water over the injured spot, so as to dilute and wash awa); 
the irritating substance, just as she pours out tears to wash 
a speck of dirt away from the eye. Alcohol attracts water 
to itself, and thus its power to do harm is greatly lessened. 
But this protection is only partial. If only a small amount 
of strong drink is used steadily for some time, nature 
becomes exhausted in her efforts of defense. Thus, while 
some exceptionally strong men seem able to use a large 
amount of strong drink with little harm, most men are 
greatly harmed by the smallest amounts. 

61. Cause of thirst for alcohol. — The property of taking 
away water from substances which it touches, accounts in part for the 
failure of alcoholic drinks to satisfy thirst. A dry state of the surface 
of the lining of the mouth gives rise to thirst. If this lining is deprived 
of water by an alcoholic drink, the sense of thirst still remains, although 
the rest of the body is supplied with water. Moreover, this lining is 
somewhat injured by the alcohol of every drink, and to soothe the irri- 
tation another drink is needed. So the thirst goes on, growing stronger 
with every drink. 

When he begins, no drunkard expects to use strong drink, or to 
drink more than a glass or two at a time, but his thirst always deceives 
him. and the momentary relief which drink gives him is only a deceitful 
addition to his thirst. 

62. Adulteration of alcoholic drinks. — The manufacture of 

pure alcoholic liquors is a slow and expensive process. So cheap imi- 
tations are made which closely resemble the real article in taste and 
appearance. Beer is often made from cheap rye or corn and quassia, 
instead of barley and hops. Its fermentation is often hastened by an 
excess of yeast, and then the product is preserved by adding salicylic 
acid or other substances which destroy the yeast. 

Whisky and brandy are also much adulterated. All kinds are alike 
in having a large amount of alcohol. In fact, the cheaper kinds of 
whisky and brandy contain the most alcohol. 

Often, instead of good grain or fruit, rotten fruit, peelings, and refuse 
of all kinds are used in making liquors. When distilled and treated 



48 APPLIED PHYSIOLOGY 

with flavorings, a drink is produced which an expert chemist can 
scarcely distinguish from genuine liquor, and yet its evil effects are 
notoriously greater. 

63. Temperance drinks. — Strictly speaking, water is 
the only temperance drink, for all kinds of flavored and 
fermented drinks are designed only to please the taste and 
not to fill a want of the body. The use of any except water 
is a form of intemperance, but those which contain alcohol 
are especially harmful. 

Cider, root beer, and ginger ale, and other " homemade " 
drinks which are *' worked" or fermented, all contain 
alcohol, and should be classed as strong drink. These 
drinks are particularly bad, for their use may lead one to 
indulge in stronger drinks. 

SUMMARY 

1. A sirupy solution of sugar will not become sour, but 

will '' preserve " fruit from spoiling. 

2. Sugar in a weak solution becomes alcohol. 

.3. The change is produced by the growth of microscopic 
plants C3]\ed yeast. 

4. Sugar in weaker solution becomes vinegar. 

5. The change is produced by a collection of microscopic 

rodlike plants which form the "mother" of vinegar. 

6. Changing sugar to alcohol or vinegar is fermentation. 

7. Wine is made by fermenting fruit juice, and beer is 

made by fermenting a solution of sprouting grain. 

8. Distilled liquors are made by boiling fermented liquors 

and collecting the vapor. 

9. Alcohol prevents decay by killing the germs which 

produce rotting. 
10. Alcohol takes water away from other substances and 
then hardens and shrivels them. 



FERMENTATION AND ALCOHOL 49 

11. Alcohol disappears very rapidly after being taken 

into the body. 

12. Alcohol takes water from the lining of the mouth 

and produces thirst. 

DEMONSTRATIONS 

i8. Show fermentation by setting aside a bottle containing a little 
molasses in water. In a few days bubbles will rise, showing that fer- 
mentation has begun. Add a little yeast to another bottleful, and 
notice that fermentation begins within a few hours. Boil another 
bottleful and at once cork it tightly, and notice that it does not change. 
Explain that the first bottleful started with few germs and so fermenta- 
tion at first was slow. The second had many and fermentation began 
at once. In the third the yeast germs were destroyed and so no fer- 
mentation took place. 

19. Set aside a bottle of weak molasses and water for a week or two. 
Notice that fermentation goes on but that the liquid now tastes sour, 
for it has become vinegar. 

20. Soak a yeast cake in water for a few^ hours and examine a tiny 
drop under the microscope with a power of at least 200 diameters. 
Notice the small oval cells, from the edges of which tiny cells seem to 
be budding. These are yeast cells. In the same specimen starch 
grains will appear as much larger irregular bodies of a shape depending 
upon the kind of grain used in making the yeast. 

21. Procure some alcohol. Notice its sharp odor and taste. Show 
that it will dissolve and remove grease from the hands. Explain that 
in the arts, it is used to dissolve oils, resins, and such substances as 
water will not dissolve. Procure some wood spirits and contrast its 
odor and taste with that of common alcohol. Show that it, too, 
dissolves grease. 

22. Pour some alcohol upon the white of an egg. Notice that the 
alcohol coagulates it and turns it white. 

23. Place a small piece of tender meat in a bottle of alcohol for 
a day or two. Notice that it turns whitish in color and becomes 
shriveled, hard, and dry. Explain that the alcohol takes away the 
coloring matter of the meat, and also coagulates the albumin much in 
the same way as hemlock bark tans leather. Explain how alcohol pre- 
serves substances in this way. 

OV. PHYSIOL. — 4 



50 APPLIED PHYSIOLOGY 

24. Dip a small piece of paper in alcohol and touch it with a match. 
It bursts into a flame at once, and develops great heat but no smoke. 
Notice that the paper does not burn until the alcohol is nearly used up. 
Explain that in the body alcohol seems to be easily oxidized, and uses 
oxygen which should go to the proper food of the body. 

25. Hold a cold stone in the mouth of a teakettle or in the steam of 
a pan of water. Notice that the vapor condenses in drops upon the 
stone. This will illustrate distillation as well as a complicated appa- 
ratus of coils and running water. Explain that dew upon the grass is 
a distillation of water. 

REVIEW TOPICS 

1. Describe how alcohol and vinegar are commonly 

formed. 

2. Describe \\v^ yeast plant. 

3. T)&scYihQ mother of vinegar. 

4. 'DQS(zr]bQ fermentation. 

5. Tell how fermentation is applied to bread making. 

6. Describe malt liquors. 

7. Describe wine. 

8. Describe spirits and the process by which they are 

made. 

9. Describe alcohol. 

10. Give the three main properties and effects of alcohol. 

11. Tell what becomes of alcohol when taken into the 

body. 

12. Tell why alcohol does not satisfy thirst. 



CHAPTER V 
DIGESTION OF FOOD IN THE MOUTH 

64. Food and digestion. — Albumin, fat, and sugar are 
continually being oxidized in the body, and the products 
of oxidation, together with mineral matter and water, are 
being thrown off. In order to keep up the strength and 
form of the body a constant stream of new material must 
be supplied. 

A}iytJiuig wJiich^ taken inside of the body, supplies it with 
weighty heat, or energy is food (see pp. 64 and 89). 

In preparation for the use of the body, food is reduced to a form which 
can be dissoh-ed in water, and drawn through the walls of the blood 
tubes. The blood distributes it to all parts of the body. The process 
of producing a chemical change in food so that it can be taken up by 
the blood is digestion. 

Man uses as food a combination of albumin, fat, sugar or starch, 
mineral matters, and water, whicli are identical with the proximate prin- 
ciples of the body. Of these water and mineral matters can enter the 
blood without being changed, while the albumin, fat, sugar, and starch 
require digestion. Albumin is changed to a form called peptone^ which 
can easily diffuse through the walls of the blood tubes, and so become 
a part of the blood. 

Sugar and starch are both changed to glucose, a form of sugar found 
in the grape. Fat is saponified and emulsified. 

65. Cooking. — Digestion is begun by applying heat to 
food, either with or without water. Preparing food by 
heat is cookijig. The heat of cooking coagulates the 
albumin. It also softens and dissolves the connective 

51 



52 APPLIED PHYSIOLOGY 

tissue which binds together the cells of the food material, 
and thus makes meat and vegetables tender. It devel- 
ops an agreeable flavor which stimulates the desire for 
food and promotes digestion. Cooking has no effect upon 
fat itself, but the tiny pockets of albumin in which it is 
stored in meat and vegetables are softened or dissolved 
away, and the fat is set free. In vegetables and flour, 
starch is in tiny grains, each of which seems to be 
made up of layers of starch separated by thin layers of 
a waterproof substance. Hot water causes the starch to 
swell and burst these envelopes, and the starch itself is 
then dissolved, thickening the water to a jellylike mass. 
Cooking has no effect upon the sugar and mineral matters 
of the food, except to mingle them thoroughly with the food. 
Thorough cooking also destroys many poisons, and all 
the disease germs in tainted food. Yet cooking does not 
render tainted food fit for use. 

66. Ways of cooking. — Some foods are best cooked by being 
boiled or stewed. Other foods are best when roasted or broiled. The 
exact method is not so important as the skill of the one who does the 
cooking. 

In all forms of cooking the principles are the same. If the solid food 
alone is to be eaten, as much of the juices as possible should be retained 
in the food by coagulating the albumin upon the outside at once so as to 
imprison the juices. This can be done by having the water boil before 
the food is placed in the kettle, or by placing the food in a hot oven. 
The film which forms upon the outside of the food effectually seals the 
juices within. If both the solid food and the liquid in which it is 
cooked are to be eaten, the flavors are better developed if the juices are 
diffused through the liquid. In this case the food should be placed in 
cold water or a cool oven, and heat applied gradually so as to avoid 
coagulating the exterior sooner than the interior. In most cases the 
food will be of better quality and taste if the cooking is done slowly. 
When the heat is continued after the food is thoroughly softened, its 
fibers are apt to become hard and dry. 



DIGESTION OF FOOD IN THE MOUTH 



53 



As a general rule it is best to cook each kind of food separately. 
Each substance can then be cooked in its own peculiar manner. In 
roasting and broiling, the fat drips away. The outside of the meat, 
subjected to a high degree of heat, becomes hard, imprisoning the 
juices within. The inner part of the meat is protected from the heat 
and is cooked at a lower temperature 
than the outside. So its juices remain 
in a more natural state. 

When food made from vegetables or 
grain is baked, a crust forms upon the 
outside. This consists of hardened albu- 
min mixed with starch, which is partly 
changed by the heat to a kind of sugar. 
If the crust is not too much cooked and 
dried it is palatable and easily digested. 

67. The alimentary canal. — 

Food is taken into the body and 
digested by means of a tube lead- 
ing through the body. Beginning 
at the upper end, the parts of this 
tube, which is called the alimen- 
tary canal, are the mouth, phar- 
ynx, esophagus, stomach, and 
intestine. 

68. The mouth.— The food is 
held in the mouth for a few sec- 
onds while it is mixed with the 
watery fluid called the saliva, and 
ground fine by the teeth. This 
grinding is mastication, and the mixture with saliva is in- 
salivation. In these two processes, the teeth, tongue, 
cheeks, lips, and salivary organs all take part. The 
roof of the mouth is formed by the bony palate in front, 
and the soft movable palate behind. It is bounded on 
the sides and in front by the teeth, cheeks, and lips. 




mi 

The alimentary canal. 



54 



APPLIED PHYSIOLOGY 



The floor is formed by the tongue and the lower 
jaw. 

69. The jaws. — The lower jaw is a semicircular bone, 
whose hinder extremities are curved upwards. Each tip 
forms a hinge which turns in a socket just in front of the 
ear. It carries a semicircle of teeth, which exactly fit 
against a similar semicircle upon the upper jaw. The 
lower jaw is moved by powerful muscles in three direc- 
tions : first, up and down ; second, sidewise ; third, back- 
ward and forward. 

The upper jaw is a strong bone of irregular shape, firmly 
fixed to the rest of the skull. Its interior is hollowed out 
to form a cavity called the antrum^ which has a small 
opening into the nose. The upper ends of the teeth some- 
times project so far upward as to make slight elevations 
upon its floor. Sometimes an inflammation or abscess of 

a tooth may extend to the 
antrum, so that it becomes 
filled with pus, producing a 
very serious trouble. 

70. Teeth. — The teeth are 
hard, bony pegs set deeply 
into the lower jawbone and in 
the edge of the hard palate. 
There are sixteen on each 
jaw. Counting from the mid- 
dle of the front of each jaw, the 
first two on each side are like 
chisels, so as to bite or gnaw 
off the food, and are called the 
incisors. In a squirrel, they 
are long and sharp, so as to gnaw through wood. The 
third tooth is the canine. It is a round, firmly set tooth, 




The teeth at the age of six and 
one half years. /, the incisors; 
O, the canine ; M, the molars ; the 
last molar is the first of the permanent 
teeth ; F, sacs of the permanent in- 
cisors ; C, of the canine ; B, of the 
bicuspids ; N, of the second molar ; 
the sac of the third molar is empty. — 
Marshall. 




DIGESTION OF FOOD IN THE MOUTH 55 

which in animals is the tusk. The next two are larger, 
with flat surfaces ; they are called bicuspids. The next 
three, the grinders, or molars, have large, flat surfaces, 
well adapted to grinding the food. 

In a young child the two bicuspid teeth resemble the molar teeth in 
the adult, and the three molars are absent. At about the age of six, a 
whole new set of teeth begins to grow beneath the first teeth, and to 
press against their roots, cutting off their food supply. The blood 
takes away the substance of the old teeth as the new ones advance 
against them, until their projecting parts alone are left attached only by 
the gum. They finally drop out, while the new ones 
advance to take their places. The first teeth, like 
the permanent set, may decay and cause toothache, 
and should have as good care in filling and cleaning 
as is given to permanent teeth. 

Sometimes when a baby's gums are being cut 

through by the growing first teeth, they are tender 

and swollen, making the child fretfiil. Yet teethino^ 

, , • 1 • u uu u-i^ Section of a tooth, 

seldom causes sickness m a healthy child. 

a enamel. 

71. Composition of teeth. — The teeth ^ dentine. 

c pulp cavity con- 
are composed 01 a very hard kind 01 bone taming blood 

called dentiney which in some larsre animals *"^^^ ^"^ 

nerves. 

is called ivory. It is nourished by blood d cement. 
tubes and nerves, which enter at the tip 
within the jaw and form a pulplike mass in a small cavity 
in the center of each tooth. The root of the tooth is set 
into a socket in the jawbone, and a kind of soft bone, 
called the cement, fixes it in place. The projecting part of 
each tooth, called the crown, is covered with a hard shell 
called the enamel. 

72. Care of teeth. — When the enamel is too thin, or is worn or 
broken off, the dentine beneath it may decay. Then the tooth rapidly 
goes to pieces, often with much pain. Picking the teeth with pins and 
cracking nuts often break the enamel. Dirt and particles of food be- 
tween the teeth are great promoters of decay. The saliva deposits a 



56 



APPLIED PHYSIOLOGY 



brown substance called tartar, which may press the gum back from the 
root of the tooth, until a part of the tooth below the enamel is reached. 
Then the tooth may decay and break off at the gum, or the gum and 
bone may be forced back from the crown until the tooth becomes loose 
and drops out. Thoroughly brushing the teeth twice a day with a 
tooth brush and water is necessary for preserving the teeth. Particles 




The tougue. 

of food between the teeth should be removed, either by a soft wooden 
toothpick or else by passing a strong thread between the teeth. Still, 
with the best of care, some decayed cavities may develop, and these 
should be filled at once. With this care, almost any set of teeth should 
last a lifetime. 

The cheeks and lips are thin layers of skin and muscles, 
which can be moved freely in all directions. 



DIGESTION OF FOOD IN THE MOUTH 



57 



The tongue is a long, flat muscle, attached at its back 
end only, while its front part is capable of varied and pre- 
cise movements in every direction. 

73. Mucous membrane. — The cavity of the mouth is 
everywhere hned with a thin membrane, directly continu- 
ous with the outside skin. It consists of a loose network 
of cells carrying blood tubes and nerves. It is covered 
with a layer of flat cells, called epitJielium. Into the loose 
tissue beneath the epithelium, there project pockets or 
tubes lined with cells directly continuous with the epi- 
thelial cells of the sur- 
face of the mouth. In 
health, the cells of each 
of the tubes and of the 
surface of the mouth pro- 
duce just enough of a 
thin, clear liquid, called 
nuiciis, to moisten and 
lubricate the surface of 
the mouth 
brane is called a niiicojis 

vtembrane. It is continued into the stomach and intestine, 
and into the windpipe and lungs. 







Mucous membrane (x 200). 

a cells and loosely woven fibers forming the 
main part of the membrane. 
q-i . b mucous glands cut across. 

1 niS mem- ^ epithelium upon the surface. 



Mucous membrane is modified skin turned in from the surface of the 
body to line the interior of all the cavities which communicate directly 
with the air. Every such surface is covered by an unbroken layer of 
epithelial cells. Wherever the epithelial cells are absent, the spot is 
raw and sore. The epithelial cells of the surface of the mucous mem- 
brane are designed mainly for protection ; but those which reach into 
the tubes are set apart for the special work of producing mucus from 
material supplied by the blood. 



74. Gland and secretion. — A collection of pockets or 
tubes Uned with epithelium which forms a substance out 



58 



APPLIED PHYSIOLOGY 



of the blood is a gland. The substance formed is called a 
secretion. The epithelium of the gland does all the work 
of secreting. All the mucous membranes of the body con- 
tain glands which secrete 
^SS^ a mucus, and in addition 
many contain glands 
which secrete other sub- 
stances. 

75. Sore mouth. — 
Babies sometimes suffer 
with a form of sore mouth 
in which white specks, like 
curdled milk, appear upon 
its mucous membrane. 
The spots are due to a 
kind of mold which 
grows in milk. Gently 
washing the mouth with 
clean, warm water several 
times a day will destroy 
the mold and remove 
the sores. 

76. Salivary glands. — 
The mouth contains a 
fluid, called saliva, which 
enters it from three tubes 
on each side. Each sali- 
vary tube, after it has ex- 
tended into the flesh on 
the face for an inch or 

so, abruptly divides again and again like the branches 
and twigs of a tree. At the end of the smallest divi- 
sions, there are minute pouches ^\-^ of an inch in 




Diagram of glands. 

a epithelium upon the surface of a mucous 

membrane. 
b the epithehum continued into a simple 

tube. 
c the epithelium continued into a simple 

pocket. 
d the epithelium continued into a series of 

branching tubes and pockets. 
b, c, and d are glands. 



DIGESTION OF FOOD IN THE MOUTH 



59 



diameter. All these- tubes and pouches are rolled into 
a small mass with blood tubes and nerves. The whole 
collection is called a salivary gland. Each tube and 
pouch is lined with epithelial cells which make the saliva 
out of the fluid parts of the blood in which they are 
always bathed. The sahva flows out of the tubes into 
the mouth as fast 
as it is secreted. 
There is a sali- 
vary gland in 
front of each ear, 
called the parotid 
gland ; one along 
each side of the 
lower jaw, called 
the submaxillary 
gland, and one 
just under each 
side of the front 
endof the tongue, 
called the sub- 
lingual gland. 

77. Saliva. — 
The saliva is a 
thin, colorless, 
alkaline mixture, which often contains air bubbles. About 
YoVo P^^^ ^^ ^^^ saliva is a white substance called ptyalin, 
which has the power to change starch to glucose while 
remaining unchanged itself. Hence, ptyalin is a ferment. 
It can act only in an alkaline fluid, and its action stops when 
the food is acted on by the stomach. It digests only a 
small amount of starch, and its value is due mainly to the 
water it contains. 




The salivary glands. 



6o 



APPLIED PHYSIOLOGY 




78. Use of the water in saliva. — The water of the sahva has 
very important uses. The nerves of taste are covered by the epithelium 
of the mucous membrane, and some of the food must be carried through 
this epithelium to the nerves in order that it may be tasted. The water 
of the saliva dissolves the food and soaks through the epithelium, 
carrying a tiny amount of food to the nerves, and thus makes the sense 
of taste possible. 

During digestion, food must be reduced to a fluid condition as thin 
as milk. The saliva begins the process. Enough saliva is mixed with 

food to form a pasty mass which the 
thin walled stomach can handle with 



79. Production of saliva. — 

Saliva enters the mouth continu- 
ally, but between meals only 
about an ounce an hour is pro- 
duced, while during a meal the 
food increases in weight about 
one half by the addition of saliva. 
From one to three pints are pro- 
duced daily. The flow of saliva 
is excited by the act of chew- 
ing, and by anything held in 
the mouth, especially if it be of an agreeable taste and 
odor. Hunger, or the sight or thought of agreeable food, 
"makes the mouth water." The longer food is chewed 
the more saliva is produced. This mixing and dissolving 
action of the saliva is greatly aided by the movements of 
the various parts of the mouth. 

80. Mastication. — A morsel of food is pushed between the 
molar teeth, which crush and grind it by the three movements of the 
lower jaw. Between each movement of the jaw, the tongue and cheeks 
roll the morsel into a firm mass so that the teeth can act upon it to 
better advantage. The tongue has a delicate sensibility for the proper 
condition and position of the food, and its varied and precise move- 



A salivary gland ( X 200) . 

tube of epithelium forming the 
gland, cut lengthwise. 

tubes cut crosswise. 

connective tissue binding the 
tubes in place. 



DIGESTION OF FOOD IN THE MOUTH 



6i 



menls, aided by the movements of the lips and cheeks, keep the food 
in the best position for the action of the teeth. In a few seconds, even 
hard and dry food becomes a thin and pasty mass. The tongue col- 
lects the mass into a ball in the back part of the mouth in preparation 
for its passage to the stomach. The process of sending food from the 
mouth to the stomach is swal- 
lowing or deglutition . 

81. The pharynx. — 

Back of the tongue is a 
muscular bag about four 
and a half inches in 
length, lying against the 
spinal column and called 
the pharynx. It is lined 
with mucous membrane, 
which secretes far more 
mucus than that of the 
mouth. When the secre- 
tion of mucus is excessive 
it is called catarrJi, but it 
is usually a harmless 
affection. The pharynx 
has seven openings ; one 
into the esophagus or 
muscular tube leading to 
the stomach ; one into 
the beginning of the 
windpipe ; one into the mouth ; two into the nose, and two 
into the middle ear. The openings to the nose and ears 
can be closed by raising the soft palate against the spinal 
column. The windpipe can be closed in three ways : 
first, by the root of the tongue arching itself backward 
over the windpipe ; second, by a cover to the windpipe, 
called the epiglottis ; third, by the vocal cords sliding 




Diagram of the beginning of swallowing. 

a top of tongue. 

b pharynx. 

c morsel of food. 

d sliding door of the front of the pharynx. 

e soft palate. 

f epiglottis. 



02 



APPLIED PHYSIOLOGY 



together in the middle. The opening to the mouth can 
be closed by two upright muscles which hang between the 
back part of the soft palate and the base of the tongue. 

These two muscles come 
together in the middle 
like sliding doors. 

82. Swallowing. — By 
a conscious effort, the 
tongue quickly pushes the 
morsel of food backward 
towards the pharynx. The 
two upright muscles of 
the pharynx, gliding to- 
gether over the surface of 
the tongue between it and 
the food, cut the food off 
from the mouth. During 
this movement the phar- 
ynx closes all its other 
openings, except the one 
to the esophagus. The 
food is now beyond the 
control of the will. The 

d sliding doors of the pharynx which have ^luscleS of the pharyUX 

come together m the middle. ^ ^ ■' 

e soft palate lifted upward to shut off the nose. itSClf nOW Contract, for- 

/ epiglottis folded downward to close the ^ ^j^^ f^^^ -^^^^ ^j^^ 

larynx. ^ 

esophagus, the opening 
of which is the only one not closed. 

83. The esophagus. — The esophagus is a muscular 
tube connecting the pharynx with the stomach. It is 
about nine inches in length. It is lined with mucous 
membrane and secretes only enough mucus to moisten its 
surface. When food reaches it, a ring of the muscular 




Diagram of second part of swallowing. 

a top of tongue arched backward and up- 
ward. 

b pharynx. 

c morsel of food pushed into the pharynx by 
the back of the tongue. 



DIGESTION OF FOOD IX THE MOUTH 63 

tube contracts just above the morsel. This contraction 
runs down to the stomach, forcing the food before it as 
though a tight iron ring were sHpped down over the esopha- 
gus. A contraction of a tube within the body in a regular 
manner, producing an onward movement of its contents, 
is called peristalsis. While a horse is drinking, the peri- 
stalsis of the esophagus may be plainly seen along its 
neck. 

SUMMARY 

1. Anything which taken inside the body supplies it with 

weight or heat or energy is food. 

2. All foods are composed of one or more of the five sub- 

stances : water, albumin, fat, starch or sugar, and 
mineral matter. 

3. Food must become liquid in form and enter the blood 

tubes before it can reach the cells of the body. 

4. Cooking softens the food and develops its flavors. It 

also destroys many poisons in food. 

5. In the mouth food is ground fine between the teeth 

and mixed with the saliva so as to form a thin paste. 

6. Saliva contains a ferment which changes some of the 

starch of the food to sugar. 

7. The tongue pushes the chewed food backward into 

the pharynx. The pharynx then closes all its 
openings except the one into the esophagus. The 
pharynx then squeezes the food into the esophagus, 
and the esophagus forces it into the stomach. 

8. All cavities of the body which have an opening leading 

to the air are lined with a kind of soft skin called 
nil icons inembraiie. 

9. Mucous membrane is a network of cells and fibers 

covered with flat cells called epithelium. 



64 APPLIED PHYSIOLOGY 

10. Mucous membranes contain little pockets of epithelial 

cells, which produce a slippery fluid called mucus. 

11. A collection of pockets or tubes, lined with epithelium, 

which separates a substance from the blood, is a 
gland. 

12. The saliva is formed in three glands upon each side 

of the face. 

DEMONSTRATIONS 

26. Notice the various movements of the teeth and tongue, lips and 
cheeks, in chewing. Have one of the pupils open his mouth wide. 
Show how the soft palate which forms the roof of the mouth can be 
raised and lowered. Show the sliding doors of the pharynx, which 
reach up to the soft palate and with it form an arch over the back part 
of the tongue. Notice the small projection which points downwards 
from the summit of the arch. This is called the zivula. 

27. Have the pupils swallow slowly. Notice that the tongue, begin- 
ning at the tip, is applied to the roof of the mouth until its whole length 
touches the palate. Notice that when the back part of the th -j..i oegins 
to swallow, the food is beyond the control of the '.vl^i. Notice that 
breathing is stopped, for both the nose and windpipe are closed. 

28. Get a tooth and have it sawed in two lengthwise, so as to show 
the cavity in its interior. Get another, partly decayed, to show how the 
nerves of the interior are laid bare and exposed to injury. 

29. Procure the lower jaw of a sheep or pig. With a hammer and 
chisel split open a part of the bone to show how the teeth are set into 
the bone. 

30. Point out the difference between the skin and the mucous mem- 
brane of the lips. Notice that the two are directly continuous. Explain 
that the mucous membrane is really a modified skin, and that anything 
in the mouth and stomach is really outside the body proper just as it 
would be if it were held in the closed hand. 

31. Examine a specimen of mucous membrane under the micro- 
scope, using a power of at least 200 diameters. Notice the layer 
of epithelial scales covering its outside. Notice the network of fine 
connective tissue which makes up the main part of the membrane. 
Notice the glands. They are tubes, but are cut across in the specimen 



DIGESTION OF F0(5d IN THE MOUTH 65 

and appear as circles lined with large cells. Explain that the cells 
of the glands produce the mucus. 

32. Have a boy open his mouth and raise his tongue upward and 
backward. With a handkerchief wipe dry the space between the tongue 
and teeth. In a moment a drop of water will collect between the small 
projections near the tongue. Move the tongue slightly, and notice 
that the liquid flows in a tiny stream. Explain that this is the saliva 
flowing from the sublingual gland. 

33. Chew a piece of white bread. After a little, notice that it has a 
sweetish taste. Explain that the sweetness is due to the action of the 
ptyalin of the saliva in changing the starch to sugar. 

34. While a horse or a cow is drinking, notice the peristalsis of the 
esophagus along its neck as it swallows each mouthful. 



REVIEW TOPICS 

1. Define food 3.nd name the five classes. 

2. Tell what change each must undergo in order to enter 

the body. 

3. Tell what effect cooking has upon each class of food. 

4. Discuss the different ways of cooking. 

5. Give the parts of the alimentary canal. 

6. Describe the mo7ith. 

7. Describe "Ca^jaws and teeth. 

8. Tell how the teeth are commonly injured, and how to 

preserv^e them. 

9. Describe the cheeks, lips, and tongue. 

10. Describe a nuicous membrane. 

1 1. Define a gland. 

12. Describe a salivary gland. 

13. Describe the use and appearance of saliva. 

14. Describe mastication. 

15. Describe the /'//<2;7;/;r. 

16. Describe siuallozving. 

1 7. Describe peristalsis. 

OV. PHYSIOL. — 5 



CHAPTER VI 



STOMACH DIGESTION 



84. Cavities of the body. — A muscular partition, curved 
sharply upward, divides the inside of the body into two 

cavities, — an upper one, 
called the chest or tJiorax, 
which contains the Jieaj't, 
lungs, and the esophagus, 
and a lower one, called 
the abdomen, which con- 
tains the stomach, intes- 
tine, liver, spleen, and 
kidneys. This muscular 
partition is called the 
diaphragm. 

85. The abdomen and 
peritoneum. — The abdo- 
men is a closed cavity, 
bounded above by the 
diaphragm, on the sides 
partly by the ribs, and 
behind partly by the 
spinaf column. The bones 
of the pelvis form its floor. 
The rest of its walls are 
formed by thick sheets of 
muscles. It is lined with a very smooth membrane called 
the peritoneum. 

66 




Organs of the chest and abdomen. 

a larynx, 

b trachea. 

c clavicle, or collar bone. 

d sternum, or breastbone. 

e lung. 

/ heart. 

g liver. 

h stomach. 

i large intestine. 

y small intestine. 



STOMACH DIGESTION 



67 




The peritoneum also covers the outside of all the abdominal organs. 
Such a membrane, lining a cavity which is not in open communication 
with the air, is a serous membrane. The peritoneum is the largest and 
most important serous membrane. It is a thin, closely-woven network 
of interlacing cells covered by a single layer of flat cells, which give it 
a shiny appearance. It is moistened by a small quantity of watery fluid, 
which is not produced by glands, but is a part of the lymphatic circu- 
lation. Its smoothness per- 
mits easy movements among 
the organs of the abdomen. 

86. The stomach.— The 

stomach is the first organ 
into which the food passes 
when it leaves the esoph- 
agus. It lies mostly on the 
left side of the abdomen 
half covered by the lower 
ribs. It is a conical en- 
largement of the alimen- 
tary canal, and is situated 
between the esophagus 
and the small intestine. 
It is about twelve inches ^ duodenum. 
in length and five inches 

in diameter. It is composed of a layer of muscle covered 
with peritoneum and lined with mucous membrane. Its 
walls are from -^^ to \ inch in thickness. It is hung in 
place by a short curtain of peritoneum, which is attached 
above to the under-surface of the liver and diaphragm. 
The esophagus opens into the stomach at its upper left 
side, called the cardiac extremity. The opening into the 
intestine is at the right and narrowest part, and is called 
the pylorus. The pylorus can be closed by a thick ring of 
muscle. 



Organs in the upper part of the abdomen. 

a liver, raised up. 

b gall bladder upon the under surface of the 
liver. 

c spleen. 

d stomach. 

e pancreas ; the line passes through the com- 
mon opening of its tube and that from 
the gall bladder. 



6S 



APPLIED PHYSIOLOGY 



87. Glands of the stomach. — The mucous membrane of 
the stomach contains numerous glands which secrete a 
special digestive fluid called the gastric juice. The glands 
are short tubes each about ^\-^ of an inch in diameter, 
and -^-^ of an inch in length. The tubes are set closely 
together and resemble pinpricks in the mucous mem- 
brane. Each tube is lined with 
a single layer of epithehal cells 
which produce the gastric juice 
from material supphed by the 
blood. Besides these glands 
there are many others which 
secrete only mucus. 

88. Gastric juice. — The gas- 
tric juice is a yellowish fluid, 
and consists of water holding 
in solution hydrochloric acid 
and two ferments. These are 
the essential agents in stomach 
digestion. Hydrochloric acid is 
produced by the epithelium of 
the gastric tubes from the salt 
contained in the blood, and 
forms from -g^Vo" ^o i\-^ of the 
gastric juice. The ferments 
are white, albuminous substances produced from the blood 
by the epithelium of the glands, and form about -g-^Q of 
the gastric juice. The flow of gastric juice is promoted 
by a slow, steady in-taking of food at about the tempera- 
ture of the body. The sahva, which is sHghtly alkahne, 
an agreeable taste of the food, and a pleasant frame of 
mind also aid its flow. About three quarts enter the 
stomach each day. 




Gastric glands in the stomach 
( X 200) . 

a epithelium of the surface of the 

stomach. 
b epithelium lining the tubes of the 

glands. 
c connective tissue between the 

tubes. 



STOMACH DIGESTION 69 

89. Peristalsis of the stomach. — Anything taken into 
the stomach causes a continuous and regular movement 
of the organ, due to the alternate contraction and relax- 
ation of its muscular fibers. This is an example of slow 
peristalsis. The food is thus caused to flow in a steady- 
stream from the esophagus to the left, and then down to 
the right and back again, completing the circuit of the 
stomach in about three minutes. By this movement it is 
thoroughly mixed with the gastric juice. 

90. Ferments of the gastric juice. — One of the ferments 
of the gastric juice, rciinin, acts by coagulating milk. In 
the child this action is very important. 

The other ferment, pepsin, softens the albumin of food 
and changes its character so that it will dissolve in water 
and diffuse through the walls of the blood tubes to become 
a part of the blood. This form of albumin is 0,2^^^ peptone, 

A quarter of a grain of pepsin can render a whole white of an G^gg 
soluble. It acts best at the temperature of the body, and there must 
be an acid present. The surface of the food particles are acted upon 
first, and the products of its action are rubbed off by the peristalsis of 
the stomach, and the next layer is acted upon in the same manner. 
Some of the gastric juice penetrates between the particles of food, and 
slowly eats its way into the food mass, thus dissolving apart the sepa- 
rate cells which compose the food. Its action is confined solely to the 
albumin. In fat meat the albumimDus pockets are eaten away, and the 
fat is set free. Starch is not acted upon, except to be freed from its 
albuminous envelopes. 

The result of stomach digestion is a fluid called chyme. 
Peptone imparts to it a bitter taste, while small particles 
of fat give it a milky appearance. Food then appears as 
it would if it had been boiled for a long time. 

91. Use of the acid. — Pepsin can act only in the presence of 
the acid, in an amount at least sufficient to neutralize the alkali always 



70 APPLIED PHYSIOLOGY 

present in the food. The gastric juice is more often deficient in acid 
than in pepsin. 

Besides assisting the pepsin the acid alone can perform the first 
stages of changing albumin to peptone. Living germs of fermentation 
and disease are sometimes swallowed. The acid destroys them if it is 
present in the gastric juice in its full amount. This is a provision of 
nature to prevent fermentation from taking place in the stomach, which 
might otherwise become sour at every meal. This explains why 
diseases are more easily caught when the stomach is deranged. In 
a healthy person the germs meet the destroying acid almost at the 
entrance to the body. 

92. Amount of stomach digestion. — The stomach digests 
only albumin. The main uses of the stomach are, to act 
as a storehouse for food, to mix it with the watery gastric 
juice, and to reduce it to a form still more liquid than 
when it left the mouth. The acid prevents the food from 
spoiHng, and, with the pepsin, begins the digestion of the 
albumin. The stomach is not absolutely necessary for 
digestion, but because of its capacity it enables us to carry 
a store of food so that we do not need to eat every few 
minutes. 

93. Passage of food into the intestine. — Every minute 
or two the pylorus opens, permitting a Httle of the chyme 
to escape into the intestine, where the main work of diges- 
tion is performed. 

Some food begins to pass out of the stomach within a 
few moments after eating. The time required for the 
stomach to empty itself completely is from two to five 
hours, depending upon the amount of food and the ease 
with which it is broken up. Thus we commonly say that 
it takes from two to five hours for food to digest. 

When the stomach has been empty for some time, there 
is a sense of hunger. Yet the intestine may still contain 
enough undigested food to supply the body for hours. 



STOMACH DIGESTION 7 1 

SUMMARY 

1. The diaphragm divides the inside of the body into an 

upper cavity called the tlwrax and a lower one called 
the abdomen. 

2. In the abdomen are the organs of digestion. 

3. The Hning of the abdomen and the covering of its 

organs is a smooth membrane called peritoneum. 

4. The stomach is a muscular bag lined with mucous 

membrane and covered with peritoneum. In its 
mucous membrane are glands which produce the 
gastric juice. 

5. The gastric juice is water containing hydrochloric acid, 

and two feriJients. It changes albumin to peptone. 

6. The actions of the stomach may be summed up in three 

things: (i) It is a storehouse in which food is held 
while being passed on to the intestine in a slow and 
steady stream. (2) Its peristaltic movements break 
up the food and mix it with the gastric juice. (3) It 
digests some albumin by means of the acid and 
pepsin of the gastric juice. 

7. Every minute or two 'some of the liquefied food passes 

through the pylorus into the intestine. 

8. In from two to five hours after a full meal the stomach 

is usually empty. 

9. The stomach has no action upon starch or fat, and 

digests only a part of the albumin. 

DEMONSTRATIONS 

35. Show the internal organs of an animal. A frog or a mouse will 
do ; but a rat, a rabbit, or a cat will be better. 

Always prepare the specimen in private, and leave it before the class 
only while it is actually being shown. Cover all the parts except those 
to be shown, and wash away all traces of blood. Any small animal may 



72 APPLIED PHYSIOLOGY 

be killed quickly and painlessly by placing it in a tight box or covered 
pail and pouring in half an ounce of chloroform. Demonstrations of 
the internal organs had better be made only before those members 
of classes who wish to see them. 

36. It is well to preserve permanent specimens of the different 
organs. One part of formalin to 30 parts of water is most excellent. 
It is neither expensive nor poisonous, while it preserves specimens m 
their natural form and color. The following inexpensive mixture, 
known as Midler's fluids is also good. 

Sodium sulphate (Glauber's salt), i part, 
Potassium bichromate, 2 parts. 

Water, 100 parts. 

This forms a yellow fluid and stains the specimens yellow. It is 
only slightly poisonous, even if taken into the mouth, while soap and 
water will remove it from the hands. 

Put the specimen in a large covered earthen or glass jar, with an 
amount of the fluid equal to at least five times the bulk of the speci- 
men. Remove it from the jar to a platter when showing it to the 
class. The fluid will harden the tissues so that even soft organs may 
be handled with safety. 

Special training is required in preparing microscopic specimens 
showing the tissues in their proper position. The difficulty consists in 
cutting a slice thin enough ; for the microscope magnifies in thickness 
as well as in length and breadth. 

37. Open the abdomen of a dead animal by a cut from the ribs to 
the end of the body. Notice that the organs and walls of the abdomen 
are shiny from their covering of peritoneum. Notice that the perito- 
neum is thin and strong, that its appearance diff"ers from that of a 
mucous membrane, and that it can be peeled from the abdominal 
walls. (See demonstration 35.) 

38. Notice the shape and position of the stomach. Open it to show 
the folds in the mucous membrane. With a specimen of mucous mem- 
brane under the microscope show the short, straight gastric glands stand- 
ing side by side. Sketch them. (See demonstration 35.) 

39. Notice the dome of muscle extending completely across the body 
above the stomach. Explain that this is the diaphragm, and that it 
divides the body into two cavities. Open the chest and show its cavity 
and the top of the diaphragm, which separates it from the abdominal 
cavity. (See demonstration 35.) 



STOMACH DIGESTION 73 

40. Illustrate stomach action by placing small slices of hard-boiled 

egg in — 

Hydrochloric acid, 40 drops, 

Pepsin, I grain, 

Water, | pint. 

Keep the mixture in a warm place, shaking it occasionally. In a few- 
days the egg will completely dissolve. Show some powdered pepsin 
and some dilute hydrochloric acid. 

41. Boil some potatoes and meat for several hours, to illustrate the 
appearance of chyme as it leaves the stomach. 

REVIEW TOPICS 

1. Describe the two main cavities of the body. 

2. Describe the lining of tJic abdomen. 

3. Describe a serous membrane. 

4. Describe the stomach. 

5. Describe the gastric juice and the glands in which it 

is formed. 

6. Tell the name and the action of the acid of the gastric 

juice. 

7. Tell the names and the actions of the two ferments. 

8. Tell how each class of food is affected by the stomach, 

and how much. 

9. Describe the pejistaltic movements of the stomach. 

10. Tell how the food passes from the stomach into the 

intestine. 

11. Tell how important the work of the stomach is in 

comparison with the work done in the intestine. 



CHAPTER VII 
ABNORMAL ACTION OF THE STOMACH 

94. The appetite. — Eating is designed to furnish the 
body with proper nourishment, but many ''Uve to eat," 
and pay for their meals with a host of bad feehngs. The 
amount and kind of food, and the time of eating, must be 
suited to the needs of the body. A wild animal eats and 
thrives without thought of what it eats, for nature has 
given it certain signs which it follows blindly and yet 
securely. Man possesses the same signs, and if they 
were followed, indigestion would be rare. The sign of 
the need of food is the feeling of hunger and thirst, or the 
appetite. The kind of food required is indicated by the 
sense of taste, and the proper amount of food is known by 
the absence of hunger and by the sense of taste begin- 
ning to fail. 

95. Natural taste of food. — The simplest kind of food 
tastes the best to a hungry person. He eats it with keen 
enjoyment until his hunger is satisfied. If he leaves the 
table now and goes about his work, his meal will digest 
without producing unpleasant feelings. 

Food flavored only with salt has a natural taste of which 
we never tire, and which gives reliable signs as to the 
quantity needed, and the time of eating. If only this 
kind of food is placed upon the table, the sense of taste 
and the satisfied feeling at the end of the meal are reli- 
able guides as to the amount and kind of food needed. 

74 



ABNORMAL ACTION OF THE STOMACH 75 

96. Perverted appetite. — After hunger has been satisfied with 
all the food needed, a food with an artificial taste is often brought on, 
and a new appetite arises. The taste soon learns to prefer the arti- 
ficially prepared food, and the education of "living to eat'' is begun. 
Pie, cake, sweets of all kinds, spices, and seasonings are eaten mainly 
to please an acquired appetite. 

Sweets and highly seasoned food do not satisfy a hungry man as 
plain food does, but on the contrary their taste becomes sickening to 
the stomach, before they begin to satisfy his hunger. Moreover, the 
appetite for artificial things may persist after the stomach is filled. 

97. Intemperate eating. — In the hurry of business or pleasure 
men gulp down their dinners in huge mouthfuls, and overload their 
stomachs before the surprised organs can take account of the kind or 
quantity of food eaten. Some eat too much in prolonging the pleas- 
ures of taste. Nearly everybody indulges an appetite for sweets and 
highly seasoned food. Satisfying an appetite which is not the expression 
of actual need of the body is as much hitemperance as drinking strong 
drink, and leads to the same kind of serious results. 

98. Insufficient mastication. — A whole train of evils follows 
intemperate eating. When food is swallowed in large lumps instead 
of being masticated to a thin gruel, too little saliva is mixed with it. It 
reaches the stomach too dry, and so a larger amount of gastric juice is 
needed. But the saliva is the natural stimulant to the flow of juice, 
and if it is small in amount, the gastric juice does not flow in sufficient 
quantity and food is not well digested. 

99. Too much food. — An excessive amount of food stretches 
and weakens the stomach, and peristalsis cannot take place so vigorously 
as it should. The lumps of food are neither penetrated by the gastric 
juice nor ground to pieces by the peristalsis, but only their outer sur- 
faces are slowly dissolved. The food thus remains too long a time 
in the stomach, and some may stay there until the next meal. 

100. Eating between meals. — Eating at irregular hours or 
between meals also disturbs the stomach. Two or three hours after a 
meal the work of the stomach should be done, and it should be per- 
mitted to rest. If more food of any kind is eaten, the stomach must 
either be overworked or the food not be digested. 

Food which the gastric juice softens with difficulty behaves like 
large lumps of food, and finally either is vomited, or is passed on to the 
intestine to create more trouble there. 



^6 APPLIED PHYSIOLOGY 

101. Fermentation in the stomach. — The stomach cannot be 
abused in any way without suffering in all its actions. It gives expres- 
sion to its suffering by pain, headache, heart beating, and a host of other 
bad feelings. It makes the whole body weak and sick. Its imperfect 
action also permits fermentation to go on, which makes the food sour. 
Living germs like those producing alcohol and vinegar are continually 
being eaten. In health, the acid of the gastric juice destroys them, 
but when anything weakens the acid or prevents it from reaching the 
germs, they grow and produce vinegar and other acids, and also gases. 
The result is a sour stomach and " wind on the stomach," which comes 
up and out of the mouth as though it were vomited. This is a sign 
of indigestion. 

The gas distends the stomach and presses it against the heart, so that 
the beats are felt ; and then the heart and not the stomach receives the 
blame. A sour stomach is at first the result of improper action, not the 
cause; but, once developed, it may cause a greater disturbance, and 
then there is only a step to actual stomach disease. 

102. Drinking while eating. — A great part of the work 
of digestion consists in mixing food with water. When 
dry food is eaten, the gastric juice must be produced in 
large amount before digestion can begin. A glass or two 
of water, either alone or with tea or coffee, aids the action 
of the gastric juice. If the water is not used in place of 
saliva in moistening the food, or is not employed to hasten 
the act of swallowing food, drinking during meals will be 
beneficial. Many drink too Httle liquid. 

103. Hot or cold food. — ■ Food either too hot or too cold 
hinders the production and action of the gastric juice and 
disturbs peristalsis, so that the movements of the stomach 
may not resume their natural course until a long time after 
the temperature of the food becomes that of the body. 
A glass of ice water may remain perceptibly cold to the 
stomach for from one quarter to half an hour, and its 
effects upon the movements of digestion may last much 
longer. 



ABNORMAL ACTION OF THE STOMACH 77 

104. Rest and eating. — When the body is very tired, 
the stomach has not the proper energy for digesting food. 
If food is eaten just as a person comes home fatigued by 
a hard day's work, there is apt to be a night of pain and 
indigestion. If, before eating, a glass of warm water or 
coffee or milk is taken, followed by a short nap, so as to 
rest the body, the meal will be enjoyed, and digestion wdll 
go on unaccompanied by bad feelings. 

After a meal the stomach requires an extra amount of 
blood and energy. A rest of fifteen minutes after each 
meal would be a great health saver. 

105. Rules for eating. — Chew each mouthful to a paste 
and sw^allow^ it before taking another. 

Stop as soon as the taste of plain food begins to pall. 
Allow four or five hours to elapse before eating again. 

SUMMARY 

1. Hunger indicates the need of food, and taste indicates 

the kind. 

2. When only plain food is eaten, these tw^o signs are cor- 

rect guides in eating. 

3. An appetite for sweet and highly seasoned food may per- 

sist after hunger has been satisfied with plain food. 

4. Sweet and seasoned foods soon disgust the sense of 

taste, thus showing that they are not needed. 

5. Eating food for mere pleasure is intemperance. 

6. Eating too much, too rapidly, or too often is intem- 

perance. 

7. As a result of intemperate eating, acid fermentation 

often occurs in the stomach, producing discomfort 
and sickness. 

8. A person should eat only plain food, slow^ly, and at 

intervals of not less than four or five hours. 



•J^ APPLIED PHYSIOLOGY 

DEMOnSTRATION 

42. Nearly every one has felt the effects of intemperate eating. 
When " stomach sick/' a sharp-tasting gas and very sour food often 
come up to the mouth, showing that acid fermentation is going on. 
Notice how plainly a person feels his own heart beats after a large meal, 
owing to the pressure of the distended stomach upon the heart. 

REVIEW TOPICS 

1. Tell how a person knows when and how much to eat 

or drink. 

2. Define an appetite and tell how it can be satisfied 

naturally. 

3. Illustrate an artificial appetite and tell how it can be 

distinguished from a natural appetite. 

4. Tell some of the ways in which men abuse their stom- 

achs by indulging their artificial appetites. 

5. Tell some of the effects of too rapid eating; of imper- 

fect mastication ; of overeating ; of eating between 
meals. 

6. Tell how food sours within the stomach. 

7. Tell how drinking at meal times is beneficial, and in 

what way it can be harmful. 

8. Tell how hot or cold food affects the stomach. 

9. Give some simple rules for eating. 



CHAPTER VIII 



INTESTINAL DIGESTION 



i^'-'s^'^ 



106. The intestine. — The part of the alimentary canal 
below the stomach is called the mtestmc. The intestine is 
a tube of varying size, 



whose different parts 

have different names. ii^^flH^lk '\ 

Next to the stomach 

is the small intestine, 

which is about one 

inch in diameter and 

about twenty feet in 

length. It opens into 

the la7'ge intestine, 

which is about two 

inches in diameter and 

five feet in length. 

107. The small in- 
testine. — The small 
intestine is very movable, and is coiled in the abdomen in 
no definite order. It is held in place by a fanlike fold of 
peritoneum, called the mesentery. The mesentery is about 
four inches in length along its back edge, which is fastened 
to the spinal column, and twenty feet at its outer edge, to 
which the intestine is attached. Its breadth from the spinal 
column to the intestine is about four inches. 




Diagram representing a cross section of the 
small intestine, showing the three layers, and 
the way in which the blood tubes pass be- 
tween the two folds of serous membrane (the 
peritoneum) which forms the mesentery. 



79 



8o 



APPLIED PHYSIOLOGY 



In front of the intestine, and partly enwrapping its folds, is a thin 
apron of peritoneum, called the 07nentu7n. It contains much fat, and 
acts as a cushion and as protection against cold. The small intestine 
for about ten inches from the stomach is called the duodenum. Then 
for about eight feet it is called the Jejuutun, and the remaining eleven 
feet is called the ileiun. There is no very marked difference between 
any two sections of these divisions. 

The intestine ends at about the level of the hip bone, 
and opens into the side of the large intestine by a slitlike 
valve, which permits matter to pass into the large intes- 
tine, but to a great extent prevents its backward movement. 

108. The large intestine, or colon. — The whole large 

intestine is called the 
colon. Its beginning 
is a small pouch called 
the ccBcum^ which is 
situated on the right 
side of the abdomen 
at the level of the hip 
bone. 

From the caecum 
there extends a small tube one quarter of an inch in 
diameter and two inches long, closed at its outer end. 
This tube is called the vermiform appendix. It sometimes 
becomes inflamed, forming an abscess, and produces the 
disease called appendicitis. 

The colon extends upward to the ribs, then crosses the 
abdomen to the left side, and then extends downward. 
These parts are called the ascending, transverse, and de- 
scendijtg colon. The colon is held in place by a narrow 
fold of peritoneum. It is not an even tube, but looks as 
though strings were tied about it at intervals of a few inches. 

109. Structure of the intestine. — The whole intestine 
consists of a tube of muscular tissue, whose walls are 




A piece of intestine showing the folds of the 
valvulae conniventes upon its inner surface. 



INTESTINAL DIGESTION 8 1 

from ^Q to I of an inch in thickness. It is covered with 
peritoneum and lined with mucous membrane. Its muscle 
fibers extend both lengthwise and circularly. In the mucous 
membrane of the small intestine are folds, eacn of which 




i-c/ 



Villi (X 200). 
a epithelium upon the surface of the villi. 

6 connective tissue fibers which support the blood tubes and lacteals. 
c connective tissue ceils. 
d glands which form the intestinal juice. 
e intestinal gland cut across. 

extends from one half to three fourths the way around the 
intestine. The folds are called valvnlce conniventes. Upon 
the surface of each fold are finscerlike projections called 
villi, which are from -^ to i of an inch in length, and 
from ^\^ to y^Q- of an inch in diameter. Between the bases 
of the villi minute tubes, ^ J-q of an inch in length and g^ 

OV. PHYsIOL. — 6 



82 



APPLIED PHYSIOLOGY 



of an inch in diameter, extend into the mucous membrane. 

Each tube is hned with a layer of epitheUal cells, which 

secrete a fluid called the intestinal jtcice. 

110. Villi. — Each villus consists of an outer covering 

of epithelial cells, inclos- 
ing a loose meshwork of 
fine blood tubes, and also 
of tubes called lacteals, 
both of which take up 
the food as it is di- 
gested. Neither villi nor 
valvulae conniventes are 
found in the large intes- 
tine. 

111. The pancreas. — 
From the duodenum there 
extends a very short tube, 
about the size of a small 
quill. This divides into 
two tubes, one of which 
goes to the liver and the 
other to the pancreas. 

Diagram of the essential parts of a villus. The pancreas is a gland 

a epithelium which takes up food and trans- about an inch in diameter 

ports it to the tubes within. and six iuchcS loug, lying 

b an artery. c capillaries. a a lacteal. o' y o 

behind the stomach. In 
lower animals it is called the sweetbread. Its structure 
resembles that of a salivary gland. It secretes a thin, 
watery liquid called the pancreatic jnice, which is poured 
into the intestine at the rate of one and a half pints a 
day. 

112. The liver. — The liver is a firm, dark-red, wedge- 
shaped organ, lying under the lowest ribs upon ,the right 




IXTESTINAL DIGESTION 



S3 



side. It is covered with peritoneum and hung closel} to 
the diaphragm and the spinal column. 

The tube leading from the intestine to the liver divides 
again and again into branches called M/e ducts, the small- 




A thin slice of liver (x 200). 

a veins bringing blood to the liver. c liver cells. 

d capillaries between the liver cells. d vein to carry blood away from the liver. 

e tubes to carry away bile. 

est of which are exceedingly minute, and barely recog- 
nizable with a microscope. The walls of the smallest of 
these ducts are composed of large cells of irregular shape, 
which crowd one another so that the bile tubes are almost 
closed. These cells make up the greater part of the liver. 
Among these tubes there run many fine blood tubes, in 
such a manner that the cells seem to be arranged around 



84 APPLIED PHYSIOLOGY 

the capillaries instead of around the bile tubes. Each cell 
makes bile from the blood and pours it into its bile tube, 
down which it runs, uniting with streams from other tubes. 
All the tubes finally unite their streams in the single bile 
tube which leads to the intestine. A side tube leads from 
the large bile tube to a bladder on the under side of the 
liver, called the gall bladder, which stores the bile when it 
is not needed in the intestine. 

113. Bile. — Bile is a thick, golden-colored liquid of a 
very bitter taste. It consists of waste albuminous matter, 
coloring substances, and mineral matters dissolved in water. 
Although it is a waste product, it has very important uses 
in digestion. About a quart is produced daily. 

114. Intestinal fluids. — As the food enters the intestine 
it finds three new substances ready to act upon it. These 
substances are the intestinal j?nce, th.Q pancreatic jnice, and 
the bile. All these liquids are alkaline, and tend to neu- 
tralize the acid in the food as fast as it comes from the 
stomach. 

115. Intestinal juice. — The intestinal juice is small in 
amount, and contains ferments which change starch to 
glucose, and albumin to peptone ; but its action is slight, 
and the amount digested by it is small. 

116. Pancreatic juice. — The pancreatic juice is a liquid 
of which five per cent is made of three ferments which 
perform the main part of digestion. As the chyme comes 
from the stomach, it contains albumin, some already di- 
gested, but much only softened and broken up. It also 
contains fat and starch unchanged. 

One of the ferments of the pancreatic juice, trypsin, 
acts upon the undigested albumin, changing it to pep- 
tone. 

Another ferment, amylopsin, changes the starch and 



INTESTINAL DIGESTION 85 

sugar to glucose. It does practically all the work of 
digesting starch and sugar. 

The third ferment, stcapsin, saponifies some of the fat 
with the soda and potash of the chyme. About one half 
an ounce of soap is thus formed daily. It acts as a lubri- 
cating and cleansing agent. The ferment also emulsifies 
the remainder of the fat. 

117. Action of the bile. — About a quart of bile is poured 
into the intestine each day. It has a slight power in emul- 
sifying fat, and in converting starch into glucose, but while 
its direct action is small, it does a great amount of work in 
helping and stimulating all the processes in the intestine. 
It almost doubles the power of the pancreatic juice. It 
acts as a lubricant to enable the food to slip down the 
intestine easily. It stimulates the peristalsis of the intes- 
tine, and prevents the growth of germs of fermentation. 
It also enables digested food to pass more readily from 
the intestine into the blood tubes. When bile is of poor 
quality, or too little in quantity, digestion is less perfectly 
performed, and headaches, mental dullness, and all the 
symptoms called biliousness result. 

118. Peristalsis. — The intestine shows peristaltic move- 
ments Uke those in the esophagus. A half an inch or so 
of muscle fiber, running lengthwise of the intestine, con- 
tracts, pulling the next lower part of the intestine up over 
a lump of food. Then the circular fibers contract, squeez- 
ing the food down the tube, while the fibers next below 
repeat the process, as the first ring of contraction relaxes. 
So the contraction runs down the tube, forcing the intestinal 
contents before it. 

This peristalsis is a slow, gentle movement. By it the intestinal 
contents are mixed with its juices, and slowly propelled toward the 
large intestine, where it is propelled still more slowly. 



86 APPLIED PHYSIOLOGY 

119. Result of intestinal digestion. — By the action of 
the three digestive fluids, the food is dissolved and reduced 
to a thin, milky form, called chyle. As all food contains 
many substances wholly indigestible, some solid particles 
will still remain in the chyle. Digestive action goes on 
during the whole time that food remains in the intes- 
tine, but most of the work is done in the small intestine. 
As it slowly passes down the tube, the liquid parts are 
taken up until, when it reaches the large intestine, it has 
become semi-solid again. The expulsion of the solid 
waste which finally remains is the last act of digestion. 
It takes about twelve hours for food to pass the length of 
the small intestine, and thirty-six hours to traverse the 
large intestine. 

120. What becomes of the ferments. — After the ferments of 

the gastric, pancreatic, and intestinal juices have done their work of 
digestion, they are probably digested by the new ferments poured out 
at the next meal, for they are albumin. Bile is a waste product, yet 
some of its parts are taken up by the blood and carried to the liver, and 
again poured into the intestine. Thus nature is as economical as 
possible with the resources of the body. 

121. Perfection of the digestive organs. — The mouth is 
perfectly adapted to masticating just such food as the 
stomach can readily digest, while it cannot grind such 
food as corn or hay. The stomach seems a weak, flabby 
organ, but nature made it of just the right size and strength 
to do its own proper work. 

The bile is a waste product of the body and yet it is 
one of the most important agents in digestion. In brief, 
each part of the digestive system is perfectly adapted to 
its own work. In lower animals the digestive organs are 
somewhat modified so as to adapt them to different foods 
and different modes of eating. 



INTESTINAL DIGESTION 8/ 



SUMMARY 

1. From the stomach the food passes into a long, coiled 

tube called the intestine. 

2. In the intestine the food is acted upon by ferments in 

three fluids : the intestinal juice, Xho. pa?iciratic juice, 
and the bile. 

3. The intestinal juice has a slight action in changing 

starch to sugar, and albumin to peptone. 

4. The pancreatic juice does the main part in changing 

starch to sugar and albumin to peptone, and of 
emulsifying and saponifying fats. 

5. The bile greatly increases the power of the pancreatic 

juice. It also lubricates the intestine, prevents fer- 
mentation, and aids the passage of digested food 
into the blood tubes. 

6. The muscles of the intestine slowly force the food 

down the tube so that it takes about twelve hours 
for food to traverse the small intestine, and thirty-six 
to traverse the large intestine. 

DEMONSTRATIONS 

43. Open the abdomen of a dead animal. Notice the thin, gauze- 
like omentum containing lumps of fat, and enveloping the intestine. 
Lift it up, and notice that the upper part of the large intestine seems to 
be inserted through it as though it were split into two leaves. Notice 
the difference between the small and large intestine in position, shape, 
and movability. Notice the beginning of the large intestine and the 
caecum. The vermiform appendix can usually be found also. Notice 
the position, size, and feeling of the liver, and the gall bladder beneath 
it. By careful search the pancreas can be found behind the stomach, 
lying crosswise of the body, flattened out upon the backbone. It is 
covered witli peritoneum and fat. and so is obscured, but can be recog- 
nized by its nodular appearance. A pig's sweetbread has much the 
same appearance as a man's pancreas. (See demonstration 35.) 



88 APPLIED PHYSIOLOGY 

Notice the thin fanlike mesentery, holding the coil of intestine in 
place. Notice the blood tubes running across it. Open the intestine 
for a few inches to show the folds of the valvulae conniventes. 

44. The villi are too soft and too small to be seen without a specially 
prepared specimen. A magnifying power of 50 will show them. 

Examine also a specimen of the liver, using at first a power of 100 
diameters. Notice the capillaries converging toward central veins. 
The bile ducts are too fine to be seen. 

Next use a power of 400 diameters, and examine the cells carefully. 
Notice their large size, and that they sometimes have more than one 
nucleus. Make a sketch of a villus and of the liver cells. 

45. Pour some oil into a bottle of water. Shake well, and notice 
that the two cannot be made to mix. Now add a small pinch Qi pancrea- 
tine. Shake once more, and notice that the oil now forms an emulsion 
with the water. 

Explain that the pancreatine contains the ferment of the pancreatic 
juice, and that it has the same action outside the body that it does 
inside. 

46. Make a little starch paste. While it is warm stir in a small 
pinch of pancreatine. In a few minutes the paste becomes fluid from 
the conversion of starch to sugar. 

47. Procure some bile. That from a chicken's gall bladder will do. 
Pour some into a bottle with oil and water, and notice that it forms an 
emulsion. 

REVIEW TOPICS 

1. Describe the intestine and its various divisions — the 

small and the large intestine, the caecum, the vermi- 
form appendix, the colon, the mesentery, and the 
omentum. 

2. Describe the pancreas. 

3. Describe the liver. 

4. Describe the bile and its uses. 

5. Describe the pancreatic juice and its three ferments, 

and their uses. 

6. Describe the intestinal juice and its use. 

7. Describe the peristalsis of the intestine. 



CHAPTER IX 
ABSORPTION AND ASSIMILATION 

122. Absorption of food. — Digested foods which be- 
come part of the body are peptone, glucose, and emulsifieei 
fat. While they remain in the intestine, they are still 
outside of the body proper. In order to nourish the body, 
they must dialyze through the wall of the intestine and 
become part of the blood. The process of taking any sub- 
stance into the blood is absorption. 

The bodies of most cells are semi-fluid and jellylike. 
The peptone and glucose, dissolved in water, will soak into 
the soft epithelial cells lining the intestine, while the 
original albumin and starch or sugar will not. Blood tubes 
run so near the inner surface of the wall of the intestine, 
that only a layer of epithelium and the capillary wall, 
both together thinner than the thinnest paper, separate 
the blood from the food in the intestine. The food soaks 
through the epithelial cells and the walls of the blood tube, 
and is washed away by the blood stream. So there is a 
steady flow of digested food through the epithelial cells 
toward the blood tube ; while the undigested food remains 
behind. The cells are ahve, however, and to a degree 
select what they transmit. Common salt is necessary in 
the process, and bile greatly aids it. Peptone and glucose 
are thus absorbed from the intestine by every point of its 
mucous membrane. The millions of villi projecting into 
the intestine greatly increase the surface for absorption, 

89 



90 



APPLIED PHYSIOLOGY 



while their thin walls are especially designed for the easy 
passage of fluid. 




Diagram of the course of food in its absorption and assimilation. 

123. Absorption of fat. — Fat also diffuses in the alka- 
line solution contained in the intestine. Under the micro- 
scope, particles of emulsified fat may be seen inside the 
epithelial cells of the villus. Only a small part enters the 



ABSORPTION AND ASSIMILAFION QI 

blood tube of the villus, while its greater part enters 
the lacteal tube. These lacteals unite to form larger and 
larger tubes, which run across the mesentery, and finally 
open into a single tube, the tJioracic duct, running up the 
spinal column. This is a tube as large as a goose quill, 
and opens into a large vein at the root of the neck, where 
emulsified fat from the intestine first reaches the blood. 

124. Completion of digestion. — Reckoning the amount of 
saliva as two pints a day, of gastric juice as eight pints, of pancreatic 
juice one and a half pints, and bile as two pints, and of food three pints, 
the liquid introduced into the intestine daily amounts to two gallons at 
least, and nearly the same amount is absorbed. More and more of this 
liquid is absorbed as the food passes down the intestine, until, about 
twelve hours after eating, what is left of the food and digestive fluids 
reaches the large intestine in a semi-solid state. In the large intestine 
absorption and peristalsis are so very much slower, that from twenty- 
four to thirty-six hours are required for the remains of food to traverse 
it. Its water and digested food and some of the bile are absorbed, 
while the rest of the bile and its other waste products and undigested 
matter are left behind. In health the intestine expels the waste matter 
regularly at least once a day. 

125. Assimilation of fat. — Changing the digested food 
into the various fluids and tissues of the body is assimila- 
tion. The thoracic duct pours the digested fat into a large 
vein on the left side of the neck, whence it is carried with 
the venous blood to the lungs. Little or no fat can be 
found in the blood leaving the lungs unless it has been 
eaten in excessive quantities. It is probably oxidized at 
once to carbonic acid and water, an ounce requiring three 
ounces of oxygen. It is unHkely that any fat from the 
food is stored up, but the fat in the body is probably 
derived from the albumin of the cells. The oxidation of 
fat produces heat, and the heat may be changed to power, 
or be used simply to warm the body. 



92 APPLIED PHYSIOLOGY 

126. Assimilation of glucose. — Glucose enters the blood 
in the villi, and is carried from there to the liver by means 
of a large vein called the portal vein. As the blood 
emerges from the liver, it contains almost uniformly yoVo" 
part of glucose, no matter what amount of sugar is in the 
portal vein. The liver contains a sugarlike substance 
called glycogen, which increases in amount after digestion, 
and almost disappears a few hours after eating. So it is 
thought that glucose is stored in the liver as glycogen, and 
given up to the blood in a steady stream. 

In the blood the glucose is all oxidized to carbonic acid 
gas and water, giving out heat and energy. One ounce of 
glucose requires about one and one fifth ounces of oxygen 
to oxidize it completely. 

127. Assimilation of peptone. — Peptone is a poison to 
the body and must be changed immediately after entering 
the circulation. It is carried directly to the liver by the 
portal vein, and there all becomes changed back to forms 
of albumin which will not diffuse through a blood tube, 
except under pressure. The liver further makes the albu- 
min a living part of the blood. Some albumin is oxidized 
in the liver, but a large part is carried to the cells of the 
body. Each cell in the body is thus bathed in albuminous 
food brought to it by the blood. 

Like an ameba, each cell chooses as much of the albu- 
min as it needs for food, and, taking it in by any part of 
the surface of its body, makes it a living part of itself. 
Finally, even the living albumin of the cell is oxidized, an 
ounce requiring one and one half ounces of oxygen. 

128. Absorbed poisons thrown out by the liver. — Fermen- 
tation in the intestine produces injurious substances, and 
the bile brings in waste matter. Decayed food, too, con- 
tains poisons. All these substances may be absorbed and 



ABSORPTION AND ASSIMILATION 93 

carried to the liver, which either destroys the poisons or 
sends them back to the intestine along with the bile. In 
this way the liver is a continual protection to the body. 

129. Summary of the work of the liver. — The liver serves 

as the regulator of the body. The bile which it produces is to the 
intestine what the acid is to the stomach. It aids the action of the 
digestive ferments and hinders other forms of fermentation. It smooths 
the passage of food down the intestine, and aids diffusion into the blood 
tubes. The liver changes digested albumin and sugar and fits them for 
use in the blood, and intercepts poisons which may be circulating in the 
blood. Its work goes on constantly, and upon its perfect action depends 
the well-being of the body. 

130. Biliousness. — If the liver acts imperfectly, a part 
of the peptone remains unchanged ; other poisons, too, 
brought from the intestine by the blood are not destroyed ; 
and the glucose is not properly assimilated and oxidized. 
A coated tongue, headache, loss of appetite, and an uncon- 
querable feeling of dullness follow, and are symptoms of 
w^hat is known as bilio2is7tess. 

In fevers there is a poisoning of the body by the cause 
of the disease. As the liver is one of the principal organs 
which remove poisons from the blood, it may soon be able 
to get rid of them, and thus cure the fever. But often the 
task is too great for it, and then all the symptoms of a 
severe bilious attack are added. 

131. Liver medicines. — Certain drugs, like inercury or podo- 
phyllin, have the power to increase the action of the liver. In proper 
doses they cause a great outpouring of bile which carries with it the 
poisons of the body. The drugs also cause the liver cells to assimilate 
the food more perfectly. Thus nature is assisted by the drugs and the 
biliousness is soon overcome. 

132. Intestinal indigestion. — When the stomach is over- 
worked and acts imperfectly, its work is thrown upon the 
intestine. Digestion there is imperfectly accomplished, and 



94 APPLIED PHYSIOLOGY 

fermentation takes place, with the development of poisons. 
The gas from the fermentation causes the abdomen to swell 
or bloat. The liver is imperfectly nourished, and is over- 
worked in throwing out the poisons; so it fails to make 
the proper changes in food. Then the whole body, in- 
cluding the stomach, is weakened, and biliousness is pro- 
duced. At last nature brings on severe sickness, and 
compels the overworked organs to rest. 

133. Prevention of biliousness. — Man has it in his power to 
prevent ahnost entirely the evils of indigestion. He should eat only 
plain food, in moderate quantities, ana at regular intervals. He should 
be careful not to eat when he is tired, or heated, or just before or 
after hard work. His digestive organs would then furnish a continual 
supply of perfectly digested food, sufficient for all the cells of the body ; 
the influences producing disease would be resisted by well-nourished 
cells, and sickness would be rare. 

134. Regularity of the bowels. — The last act of digestion, 
or the expulsion of waste matters from the intestine, is as 
important as eating, and should be performed with the 
same regularity. The mouth and stomach are endowed 
with feelings which make known their needs, but the 
intestine has only slight sensibility, and we are unaware 
of the digestion which is continually going on in it. Only 
when some irritating food, or a large collection of gas, 
greatly increases its peristalsis are we aware of its action. 
At a regular time every day a healthy person feels that 
the completing act of digestion should be performed, but 
the sensation will pass away if it is neglected, and in 
course of time the sensation will be repeated only once 
in two, three, or even more days. The retention of waste 
matter all that time cannot fail to do harm. Even if 
nature does not give the sensation indicating the need of 
expelling waste matter, the matters need to be expelled, 



ABSORPTION AND ASSIMILATION 95 

and the opportunity should be given daily at a regular 
time. Even if little food is eaten, the waste matters are 
still formed, and need expulsion. It should be remem- 
bered that it requires two days for food to pass the length 
of the intestine, so refraining from food only a single day 
does not make the intestine empty. 

When the intestine expels its contents too freely, there 
is usually some irritating food which it is trying to expel. 
So a dose of medicine, which will aid in its expulsion, is 
required rather than something which will restrain the 
action. 

135. Proper food. — The stomach may be able to begin digesting 
an improper meal, while the Intestine is unable to finish the work. 
Owing to the slowness with which the intestine acts, several meals 
may be eaten before its failure becomes noticeable. Then the last 
meal is blamed, instead of the offending meal. So persons may gain 
wrong ideas about the digestibility of various articles of food. 

136. Headaches. — A headache is generally due to disturbances 
in digestion. Usually when the liver is stimulated by a proper medi- 
cine, the headache ceases. Even if the headache is due to overwork, 
probably it would not have come on if the digestive organs had been 
performing their work properly. 

SUMMARY 

1. The peptone and glucose are taken up by the epithelial 

cells of the villi, and passed on to the blood in the 
capillaries inside the villi. 

2. Emulsified fat is taken up by the epithelial cells of the 

villi, and passed on to the lacteals within the villi. 
From there it goes to the thoracic duct, and finally 
is poured into the large vein at the root of the 
neck. 

3. About two gallons of fluid enter and leave the alimen- 

tary canal each day. 



96 APPLIED PHYSIOLOGY 

4. The fat is carried to the kings, and is there oxidized 

to carbonic acid gas and water, each ounce of fat 
using nearly three ounces of oxygen. 

5. The glucose is carried to the liver, and from there is 

given out in a steady stream and oxidized to car- 
bonic acid gas and water, each ounce using a little 
more than an ounce of oxygen. 

6. The peptone is carried to the liver, and there is 

changed back to the form of albumin adapted to 
the blood and tissues of the body. 

7. In the liver some albumin is oxidized, and the rest is 

sent out as a part of the blood to feed the cells. 

8. Poisons are often absorbed with the food, and are 

carried to the liver. But the liver cells separate 
out the poisons, and either destroy them or expel 
them with the bile. 

9. By intemperate eating the stomach is disordered. 

Then more work is put upon the intestine, until 
it fails in its duties. Then the liver has imper- 
fectly digested food and more poisons to take care 
of. Then a poor quality of bile is poured out. 
Then the intestine fails still more in its work. So 
the circle of cause and effect goes on, all depending 
at first upon intemperate eating. 
10. The last act of digestion, or the expulsion of waste 
matters, should be attended to regularly every day. 

DEMONSTRATIONS 

48. Show the absorption of food in a young kitten or puppy 
which had been fed with cream about two hours before being killed. 
Place the animal in a tight box along with a sponge containing half 
an ounce of chloroform. In a few moments the animal will be dead. 
At once open its abdomen and spread out its intestine. Across its 
fanlike mesentery will be seen white lines. These are lacteals, which 



ABSORPTION AND ASSIMILATION 97 

are carrying the emulsified fat from the intestine. The fluid looks 
like milk, and so the name lacteals, or milk tubes, was given to the 
tubes. (See demonstration 35.) 

49. Probably some boy in the schoolroom who is suffering with a 
bilious attack will be willing to show his tongue to the class. Notice 
that it is covered with a thick white or yellow fur. Explain that the 
tongue is a part of the alimentary canal, and that the stomach and 
intestine are in a like condition. Explain that, when the rest of the 
alimentary canal is acting well, the tongue is clean and the breath 
sweet. 

REVIEW TOPICS 

1 . Describe the diffusion of digested food into the blood. 

2. Trace a particle of digested fat from the intestine to 

the blood, and tell what finally becomes of it. 

3. Describe how the liver uses digested sugar. 

4. Describe how digested albumin becomes a part of the 

blood, and tell of what use it is to the body. 

5. Tell how the liver removes poisons from the absorbed 

food. 

6. Tell how a disturbance of digestion, in either the stom- 

ach, intestine, or liver, disturbs each of the other 
organs. 

7. Show that each organ of digestion is perfectly adapted 

to its own work. 

OV. PHYSIOL, — 7 



CHAPTER X 
ALCOHOL AND DIGESTION 

137. Summary of the action of alcohol. — The action of 
strong alcohol outside of the body is threefold. First, it 
takes away water from substances which it touches ; sec- 
ond, it hardens and coagulates albumin ; third, as a result 
of the first and second actions, it impairs or destroys the 
life of cells and of ferments with which it comes in con- 
tact. Alcohol harms the body in these ways and also has 
special effects upon parts which it does not touch. 

138. Effects upon food. — Alcohol produces changes in 
food in direct proportion to its strength and amount. If 
the alcohol be strong, and large enough in amount to satu- 
rate the food, then it may harden the albumin and render 
it more difficult of digestion. It may also prevent the 
pepsin of the stomach from acting. The habitual drunk- 
ard may take strong drink in sufficient amount and strength 
to produce this change in his food. 

139. Effects upon the mouth. — In the mouth alcohol 
may take water from the epithelial cells, and give rise to 
a sense of thirst. Although the alcohol may be mixed 
with enough water to satisfy natural thirst, yet it causes 
a false thirst to arise, which demands another drink. 

140. Effects upon the gastric juice. — When it reaches 
the stomach, a very strong alcoholic drink has a marked 
effect upon the gastric juice. The essential digestive 
agent in the gastric juice is pepsin, which is a lifeless 
albuminous ferment. The alcohol in any common form 

98 



ALCOHOL AND DIGESTION 99 

of Strong drink is in sufficient quantity to hinder or to 
stop the digestive action of the pepsin. But when the 
alcohol is absorbed or diluted, the pepsin can act as well 
as ever. 

141. Effects upon the mucous membrane. — Alcohol irri- 
tates the mucous membrane of the stomach. Then more 
gastric juice is produced in order to dilute the irritating 
alcohol. Thus the effect of the alcohol may be somewhat 
overcome by the increased quantity of the digestive fluid. 
But the alcohol may cause an increased flow of mucus 
also, just as a cold causes the pharynx to produce more 
mucus. The mucus may coat the particles of food, and 
prevent the gastric juice from acting on them. This is 
especially apt to happen when strong drink is taken con- 
tinuously in small amounts, and for long periods. In such 
conditions both the quality and q-uantity of the gastric 
juice may be impaired. 

A drink, such as even a moderate drinker often takes, 
may produce redness, swelling, and inflammation of the 
stomach. The effect is far greater when the drink is 
swallowed upon an empty stomach, for then there is no 
food to protect the mucous membrane from the direct 
action of the strong drink. 

142. Effects upon peristalsis. — The irritation of the 
alcohol at first causes an increased action of the stomach 
walls, so as to force the harmful substance away. Con- 
tinuous use of strong drink is likely to weaken the muscles 
and to make peristalsis much less. Then the food is less 
perfectly mixed with the gastric juice and is not ground to 
pieces, but remains too long in the stomach undigested. 
The water and mucus poured out diminish the strength of 
the alcohol, and this, together with the poor quality of the 
gastric juice and the long stay of food in the stomach, 



lOO APPLIED PHYSIOLOGY 

permits fermentation to take place. Thus alcohol. disturbs 
every action of the stomach, and often produces the worst 
forms of indigestion. 

It is true that a little weak alcoholic drink will not produce all these 
evil eflfects at once. Herein lies the danger. Alcohol is a deceitful 
thing. Though the stomach gives notice that it is abused by the 
drink, yet the mysterious thirst demands still more alcohol, and bribes 
its victim with the memory of its pleasant sensation. So the poor 
stomach suffers time after time, and before long becomes permanently 
crippled. 

143. Protection against alcohol. — When an alcoholic drink is 
taken into the mouth, it irritates the mucous membrane. This causes 
the saliva to flow and dilute the alcohol, so that at any one time it can 
do very little direct harm. In the stomach it causes the gastric juice 
to flow in the same way, and thus it soon becomes dilute and has little 
direct eifect. Even if the pepsin should separate from the gastric juice, 
in a little while the ferment will dissolve in the increased quantity of 
juice and perform its work well again. Nature may thus protect the 
body for some time, but it cannot remove the danger. 

144. Effects of alcohol upon the intestine. — By the time 
alcohol reaches the intestine, it is usually too dilute to 
produce much direct harm.. But if it has deranged stom- 
ach digestion, the work of digesting the food falls upon 
the intestine. Thus intestinal digestion may be imperfect. 
Alcohol itself is probably not changed by digestion. In its 
diluted form it is quickly absorbed. Even when a large 
amount is absorbed, little or none can be found in any of 
the tissues or blood tubes. The only probable way of its 
disappearance is by oxidation before it can pass beyond 
the liver. 

145. Effects of alcohol upon the liver. — Alcohol affects 
the liver in three ways. In the first place strong drink is 
apt to induce stomach and intestinal indigestion. Then 
the liver must do an extra amount of work in completing the 
imperfect digestion. Thus biliousness is often produced. 



ALCOHOL AND DIGESTION lOI 

If drinking is continued, the liver trouble is likely to 
persist. 

In the second place the destruction or oxidation of 
alcohol uses a large amount of oxygen which the liver 
should use in assimilating food. Thus food is imperfectly 
oxidized. While no products in the body can be traced 
directly to oxidized alcohol, yet when alcohol is used poi- 
sonous products of imperfectly oxidized albumin are always 
abundant. These products circulate through the whole 
body and produce far more harm than the original alcohol. 
(See p. 152.) 

In the third place the liver cells are directly affected by 
these abnormal actions. Long-continued drinking often 
results in an incurable wasting away and hardening of the 
Hver tissues. 

146. Unintentional forms of drinking. — There is a form of 

alcohol which is used by many innocently and unintentionally. Many 
a well-meaning person habitually uses '• Strengthening bitters '' after 
meals, ignorant of the fact that they are only bitter herbs dissolved in 
alcohol and water. Each dose is equivalent to a large drink of whisky. 
Essence of Jamaica ginger is only ginger dissolved in alcohol, and 
its effects are due mainly to the alcohol, and not to the ginger. 

147. Intemperance in eating. — There is a common intem- 
perance of eating too much starch and sugar. These sub- 
stances can never be digested, absorbed, and oxidized with 
sufficient rapidity to produce the intoxicating effects of 
alcohol, but their excessive use deranges the liver in the 
same manner as alcohol. In the first place, starch and 
sugar are likely to ferment and produce a sour stomach 
and intestinal indigestion ; this is probably the most com- 
mon cause of biliousness. 

In the second place, when too much sugar or other 
food is oxidized too little oxygen is left for the albumin 



102 APPLIED PHYSIOLOGY 

of the food, then the products of incomplete oxidation 
resemble those produced by alcohol ; but they usually pro- 
duce no more than a sick headache or an attack of bilious- 
ness, although under aggravated and repeated conditions 
they may endanger life. (See p. 34.) 

In the third place, the effect of a continual excess of 
food is to injure the liver cells permanently. Even the 
wasting away and hardening called "gin drinker's liver" 
may be caused by intemperate eating. Intemperance in 
eating differs from the intemperance of strong drink in 
the qicantity of effects produced rather than in their kind. 

SUMMARY 

1. Alcoholic drinks take water from the mucous mem- 

brane of the mouth and so increase the thirst, even 
if the body contains sufficient water. 

2. In any considerable amount alcohol hardens the pepsin 

in the stomach, and so prevents its acting upon the 
food. 

3. Alcohol irritates the mucous membrane of the stomach 

so that it becomes inflamed and unable to produce 
the gastric juice. Then the intestine is overworked 
in digesting what the stomach should have digested. 

4. Alcohol is quickly absorbed by the intestine. It is 

quickly destroyed, probably by oxidation, before it 
passes the liver. 

5. Because oxygen is used in the destruction of alcohol, 

incomplete and poisonous products of the oxidation 
of albumin are formed. These go through the whole 
body and greatly increase the harm done by alcohol. 

6. Bitters, and essence of ginger contain much alcohol. 

7. When starch and sugar are eaten in large amounts, 

they use oxygen which should oxidize the albumin. 



ALCOHOL AND DIGESIION IO3 

So they can produce slowly the same kind of effects 
as alcohol. 

DEMONSTRATIONS 

50. Hold some common salt in the mouth, and at once saliva flows 
to dilute it. In a moment it can be held with comfort. Explain that 
this is a provision of nature to protect the body from any irritating sub- 
stance. The stomach may pour out an excess of gastric juice in the 
same manner so as to protect the body against alcohol and other irri- 
tating substances. Call attention to other similar ways in which nature 
protects the body, as in the flow of tears to wash away a speck of dirt 
fbom the eyes. 

51. Prepare two bottles to show artificial digestion (see demonstra- 
tion No. 40). In the second one replace a quarter of the water with 
alcohol and notice that no digestion takes place in this bottle. Explain 
that this experiment may be misleading, for in the stomach more gastric 
juice will flow to dilute the alcohol until the pepsin can act as well as 
before. Explain that alcohol does not destroy the pepsin, but when the 
alcohol is diluted, the pepsin is as good as ever. 



REVIEW TOPICS 

1. Give the three characteristic actions of alcohol outside 

the body. 

2. Give the action of alcoholic drinks upon the mouth. 

3. Give the action of alcoholic drinks upon the mucous 

membrane of the stomach ; upon its secretions ; and 
upon the peristalsis of the stomach. 

4. Tell why alcoholic drinks have but little direct action 

upon the intestine and upon the villi. 

5. Give the action of alcohoHc drinks upon the liver. 

6. Explain why bitters and essence of Jamaica ginger are 

both harmful. 

7. Explain the effects of intemperate eating. 



CHAPTER XI 
DIGESTION IN LOWER ANIMALS 

148. Digestion in dogs. ^ — All four-footed animals have 
essentially the same digestive organs, secreting the 
same juices as man. Their food, also, is absorbed and 
assimilated in the same way, but there are slight modifica- 
tions according to the kind of food eaten. A dog's stom- 
ach and intestine have thicker walls, and their juices have 
f af more digestive power ; so dogs can digest even bones, 
which form one of their regular articles of diet. 

149. Digestive organs in cattle. — A horse lives upon 
hay, which man cannot digest at all. Cattle have an 
arrangement which enables them to gather a large amount 
of food at once, and then to chew it at leisure. As grass 
is eaten, it is swallowed almost whole. It goes first 
to a small intermediate stomach, and then to a large 
pouch called the paiL7ich or riLmen, which in an ox holds 
about two bushels. When this is full, the animal lies 
down and proceeds to chew the food. It forces the food 
back into the mouth in small masses, called the cud, which 
it chews and swallows again. But this time the food is 
guided on to a third stomach, whence it soon passes into 
the fourth. The fourth stomach corresponds in size and 
shape to man's, and is the true digestive stomach, while 
the others are only storehouses and passageways for the 
food. 

104 



DIGESTION IN LOWER ANIMALS 



IDS 




150. Digestive organs in birds. — Birds swallow their 
food whole, for they have no teeth or strong jaws for 
chewing. It first enters a pouch 
called the crop, where it is soaked 
in a fluid secreted there. It 
slowly passes on to the stomach, 
where it is mixed with the gastric 
juice. Then it passes into a 
muscular bag called the gizzard. 
The walls of the gizzard are from 
one fourth to one half an inch 
in thickness, and its lining is a 
thick, tough membrane. It con- 
tains small stones which have 
been swallowed. Its thick walls 
roll the food about with the 
stones, so as to grind it to pieces 
and mix it with the gastric juice. 
Then it passes into the intestine, where its digestion is 
completed, as in man. 

151. Digestive organs in insects and worms. — Insects 
possess a stomach and intestine which secrete digestive 
juices. They also have organs like the liver and pancreas. 
Some insects masticate food, and others possess a gizzard, 
which grinds the food after it is swallowed. 

Worms generally possess a digestive tube which extends 
straight through the body. Shellfish, as oysters and clams, 
possess a stomach and a coil of intestine, which passes 
through the heart. The large, dark-colored, rounded mass 
at the back end of the oyster and clam is the liver. 

152. Energy required in digestion. — Man's food requires 
but little energy in its digestion, hence most of his energy can be 
applied to physical and mental effort. To digest dog's food requires 



Digestive organs of a bird. 

a esophagus. 
b craw, or crop. 
c stomach, 
d small intestine. ' 
e gizzard. 



I06 APPLIED PHYSIOLOGY 

more energy; to digest the food of cattle requires still more. The 
lower the form of life, the more time and energy is spent in digestion, 
and the less is the action of other parts, until the lowest forms of 
animals simply live to eat, and remain at rest except when eating food. 
A comparison of man's digestion with that of the lower animals is mis- 
leading. Man's alimentary canal is designed to deal with food upon 
which but little energy need be expended. More energy is thus avail- 
able for his voluntary use. Because of his perfect food man can per- 
form more labor and undergo more fatigue and exposure in proportion 
to his size than any other animal. 

SUMMARY 

1. The digestive organs of all animals are similar to 

man's, but modified according to the needs of the 
animal. 

2. Cattle swallow grass whole, and then chew it at leisure. 

They have four stomachs. 

3. Birds swallow food whole. It passes first into the crop, 

and later is ground in the gizzard. 

4. Insects, worms, and shellfish each possess a simple 

stomach and intestine. 

5. Man uses food which is more easily digested than the 

food of any lower animal. Thus he devotes less 
time to mere eating and digesting food. 

REVIEW TOPICS 

1. Show in what way and for what purpose a dog's diges- 

tive organs differ from those in man. 

2. Show the use of four stomachs in cattle. 

3. Show how birds digest their food. 

4. Point out how the digestive organs are modified in 

worms ; in insects ; and in shellfish. 

5. Show what advantage man's food gives him over the 

lower animals. 



CHAPTER XII 

ANIMAL FOOD 

153. Food elements. — Anything which, taken inside of 
the body, supplies it with weight, heat, or energy is food. 
Man's food consists of a great variety of substances de- 
rived from the animal, vegetable, and mineral kingdoms. 
Yet all food consists of the proximate principles : water, 
mineral matter, albumin, fat, and starch or sugar. Neither 
alone makes a perfect food, but all must be present in 
proper proportions or else the body will suffer. 

154. Water. — Water requires no digestion, but is con- 
tinually entering and leaving the body unchanged in form. 
All solid food contains some water, and enough more is 
added in liquid food and in drink to supply the full needs 
of the body. Twelve or fifteen pints of fluid are used 
daily in the work of digestion, but it is absorbed back 
again to the blood and so little is lost. Within reasonable 
limits, water taken at meal times aids digestion. In order 
to digest food and wash away waste matter properly, tw^o 
or three quarts must be swallowed daily. If the thirst is 
satisfied with pure water, there will be little danger of 
taking too much, and the indications of thirst will be the 
most reliable guide as to the times of drinking and of the 
quantity required. 

155. Mineral matters. — Mineral matters are not changed 
during digestion, and they leave the body in the same form 
in which they enter. More than enough are found in all 

107 



I08 APPLIED PHYSIOLOGY 

ordinary food to supply the needs of the body. Only salt 
needs to be added to food, but man often adds far more 
than is necessary. Since water and mineral matters re- 
quire no digestion, it makes little difference in what kind 
of food they are eaten. But albumin, fat, and starch or 
sugar require digestion, and some forms are more easily 
digested than others, so a discussion of their forms in dif- 
ferent foods becomes necessary. 

156. Digestibility of food. — In judging of the value of 
food four things must be considered : 

First. The ti7ne and energy requii'ed. — Some forms of 
food require little or no energy in their digestion, while 
others cannot be digested at all. Grass contains all kinds 
of food substances, but man cannot digest it. The com- 
bination of meat, fruit, and flour which we call mince pie 
requires far more time and energy in its digestion than 
the same substances in the form of roast meat, bread, 
and fresh fruit, or in the form of a light pudding. 

Second. The amount of indigestible matter. — All kinds 
of food contain some matter which is wholly indigestible. 
Only a little of fruit is digested. Careful experiments 
show that ordinarily at least one fifth of the albumin of 
vegetable food passes through the intestine undigested, 
while only one thirtieth of meat is thus wasted. Animal 
oil is easily emulsified and saponified, while vegetable oil 
can scarcely be changed at all, but if eaten in any quantity 
is a source of intestinal disturbance. Some wholly indi- 
gestible matter in food is valuable, for it affords something 
upon which the intestine can contract so as to force its 
contents down the tube. 

Third. The amount of energy developed by the food. — 
Fat requires a large amount of oxygen in its oxidation, 
and yields a large amount of heat and energy. Sugar 



ANIMAL FOOD IO9 

requires only one third as much oxygen and develops less 
heat and energy. So food rich in fat yields more heat 
and energy than a food rich in sugar or starch. 

Fourth. Liability to ferment. — A food requiring a long 
time in digestion is more liable to ferment than one which 
is digested in a short time. Sugar and starch ferment 
easily, while fat ferments only with difficulty. 

157. Milk. — Among all the different kinds of food milk 
seems to be most perfectly adapted for man and for many 
animals. The average cow's milk consists of 

Water ^6 per cent. 

Albumin 4 " 

Fat 4i " 

Sugar 5 " 

Mineral matter \ " 

Milk thus contains all the five different kinds of food 
substances, which, moreover, are in about the proper pro- 
portions to support life best. 

The albumin, fat, and sugar of milk each re- ^'o o°^^Oo 
quires little time and energy in its digestion, and ® o ^Oo%*''P^c 

leaves but little undigested residue. Milk is more -nO^^/^fo?) o'O^O ^ 

liable to undergo fermentation than some other o ^q^§§:^o^Po^ 

kinds of food, but the quickness of its digestion ® q 9,^Oo^rsCfo 
overcomes this objection. It develops heat and oQ,Oq*o$§o° 

energy in amounts best suited to support life, p^^ globules in milk 
Milk is thus an ideal food, and can be digested (x 300). 

when all other kinds of food are rejected. 

158. Caseine. — The albumin of milk is called caseine. 
In its digestion the rennin ferment in the stomach coagu- 
lates it in fine flakes, which the acid and pepsin dissolve to 
peptone. When much acid is present in the stomach, as 
after a meal, or when fermentation has occurred, the 
caseine is apt to be coagulated in hard lumps which dis- 



no APPLIED PHYSIOLOGY 

turb digestion, producing a bilious attack. The rennin 
ferment is produced the more rapidly when milk is hot, 
while the heat hinders the production of the acid of the 
gastric juice. So if the milk is taken hot, it will be coagu- 
lated in finer flakes, which the gastric juice can digest more 
easily. If milk is taken slowly in any form, it is coagulated 
in small amounts as fast as it enters the stomach, and so 
no large lumps can form. If taken before meals, hot and 
slowly, there are but few persons with whom milk will 
disagree. 

159. Fermentation of milk. — Many kinds of living germs are 
continually falling into milk and growing, if the temperature is warm. 
Some are germs which produce acid fermentation and turn the milk 
sour. The acid coagulates the caseine, forming clabber. Germs of 
disease also will grow in milk, especially germs of typhoid fever and of 
tuberculosis. Children are very easily affected by sour milk. Often 
the germs of fermentation grow in their stomachs, souring the food 
and producing summer coinplaint. Boiling the milk destroys the 
germs but not the poisons which already have been produced. All 
cow's milk given to babies should be heated in order to destroy the 
germs. 

160. Cheese. — Rennet is often added to milk in order to 
coagulate its caseine, which, when squeezed into a firm 
mass, is cheese. The cheese holds the fat of the milk, 
while the sugar remains in the whey. Cheese is about 
one third albumin. It contains no sugar or starch. The 
amount of fat which it contains depends upon how much 
cream was left in the milk of which it was made. It is a 
valuable article of food because of the large amount of 
albumin always present. It is easily digested by healthy 
persons. In some kinds germs are permitted to grow and 
develop various acids and flavors which make the cheese 
strong. These are somewhat harmful, but mild cheese fur- 
nishes a cheap supply of good albumin. 



ANIMAL FOOD III 

161. Butter. — When milk remains quiet for some hours, 
the fat rises to the surface in the form of cream. After 
this is removed, milk is called skim milk. Cream is made 
up of fine particles of fat, each surrounded by a thin 
envelope of caseine. When cream is shaken until the 
covering of the caseine is worn off, the fat collects in a 
form called butter. The liquid part remaining is called 
buttermilk, and does not differ much from milk, except 
that the fat is mostly removed. Butter is the most valu- 
able form of fat eaten. 

162. Value of milk. — In sickness milk is almost the 
only food which the stomach can digest at all. Only about 
one twentieth of the solid part of milk fails to be digested. 
When only milk is taken, there is but little residue upon 
which the intestine contracts, and so waste matters pass 
down the tube more slowly than when solid food is eaten. 
Those who eat much milk find it profitable to eat heartily 
of substances which, like oatmeal, leave a large undigested 
residue to sweep out the waste matters of the intestine. 

163. Adulteration of milk. — It is difficult to set a standard 
for perfect milk, for no two cows give it of exactly the same composi- 
tion. Milk which has a good quality of cream usually contains a good 
quantity of albumin and sugar and so is said to be rich. Such milk is 
yellow, in distinction from the bluish color of poor or skim milk. The 
richness of milk may be measured by observing how thick a layer of 
cream will rise in a deep glass tube full of milk. Another way is to 
determine how much solid matter the milk contains by means of a 
lactometer. This is a closed tube weighted so that it will float upright. 
As more solid matter is dissolved in the milk, it becomes heavier and 
will more easily sustain a body floating upon it. The richer the milk, 
the less the bulb and tube will sink. This instrument is called a 
lactometer. By means of it milk brought into large cities is tested by 
government inspectors, and all milk which falls below a certain standard 
is thrown away. The lactometer really records the specific gravity of 
the milk. If it falls below 1.029, i^ is considered to be either watered 



112 APPLIED PHYSIOLOGY 

or of too poor quality to be sold as good milk. While such milk may 
not be injurious, yet it is a fraud to sell it at the price of good milk. 
Skim milk is bluish in color from the loss of its cream. To make it 
the color of new milk, burnt sugar is often added, and it is then some- 
times sold as new milk. It is very apt to become sour from its being 
kept for some days. 

164. Condensed milk. — Large quantities of milk are boiled 
until its water is evaporated and the milk is like thin jelly. This is 
cojidensed milk. In order to keep it, sugar is added. Condensed milk 
contains all the nourishment of new milk, with some sugar added. It 
can safely be used in place of new milk for all cooking purposes. It is 
too sweet to be used as a drink, but babies take it readily. Still it is 
undesirable as a baby food, for it contains too much sugar. 

165. Imitation cheese and butter. — Cheese made from skim 
milk contains but little fat. It easily ferments and becomes dry, so 
that it is very indigestible. There is an imitation of butter made from 
beef fat, called oleomargarine. It scarcely can be distinguished from 
real butter. Biitterine is another imitation of butter made from beef 
fat and butter. The manufacture and sale of both kinds of imitation 
butter are permitted so long as the products are sold under their right 
names. 

166. Eggs. — Hens' eggs consist of 

Water , . 70 per cent. 

Albumin 15 " 

Fat . 14 

Mineral matter i " 

Since they contain no starch or sugar, they are not a 
complete food for man, although a perfect chicken may be 
formed out of the ^gg, as the hen furnishes heat. The 
white of Q,gg is almost pure albumin dissolved in water. 
The yolk is a mixture of albumin, fat, and water. Both 
the albumin and fat of eggs are digested with little expend- 
iture of time and energy, and develop a large amount of 
heat and energy in their oxidation. They do not easily 
ferment in the stomach and intestine, and only about one 



ANIMAL FOOD II3 

thirtieth is left over in their digestion. They are thus a 
valuable food, but yet do not rank so high as milk. 

167. Digestion of egg albumin. — When boiled for a minute 
or two, the albumin of eggs is partly coagulated to a soft, jelly like mass. 
Boiling for three minutes coagulates all the albumin to an elastic, 
slippery mass ; while after boiling for ten minutes the albumin becomes 
brittle, and is easily crushed to fine particles. 

A lump of albumin of a raw egg is digested with less expense of 
time and energy than the same sized lump of coagulated albumin, and 
the longer an egg is boiled the more energy is required to digest it 
back to a liquid form. But the raw egg has a tendency to collect 
in masses which the gastric juice cannot penetrate. 

An egg boiled for less than five minutes is usually masticated only 
to medium-sized particles, which, however, owing to their smaller size, 
may be digested sooner than the large masses of raw egg. But the egg 
boiled for ten minutes is easily chewed fine, and, owing to the still 
smaller size of its particles, is digested much sooner than small lumps 
of soft-boiled eggs or the masses of raw eggs. Thus an egg boiled 
for at least ten minutes is ordinarily the most available for digestion. 
When mixed with a considerable quantity of milk, the raw egg is pre- 
vented from forming a lump, and in this form it may digest more easily 
than a cooked egg. 

168. Quality of eggs. — Fresh eggs vary but little in composi- 
tion. In time they lose a little water by evaporation through the shell, 
which is porous. A fresh egg appears clear and pink when held in 
front of a strong light, while an old egg appears dark-colored, even if it 
has not begun to decay. It will first show a dark spot where the yolk 
settles to the side of the shell, and later will be dark all through. This 
test is reliable and is often applied in markets. The shell of a fresh 
egg is bright in color and slightly rough like common newspaper, but 
an old egg becomes duller in color and shiny in appearance like writing 
paper. Ducks' eggs are nearly like hens' eggs, except that sometimes 
they acquire a peculiar taste from the ducks' food. Nearly all kinds of 
birds" eggs, as well as the eggs of turtles, are used as food. They 
differ but little from hens' eggs. 

169. Meat. — The flesh of oxen, sheep, and hogs is the 
common form of meat. All kinds of game, fowl, fish, and 

OV. PHYSIOL. — 8 



II4 APPLIED PHYSIOLOGY 

shellfish are of the same nature. The muscles form the 
lean part of meat, but nearly every part of the animal is 
sometimes used as food. Average meat consists of 

Water 65 per cent. 

Albumin = , . 17 ' 

Fat ,,.„.. 14 

Mineral matter 4 " 

Albumin is the principal part of meat. Beef has high 
food value ; mutton, fowl, and game rank next, in the 
order named. 

170. Digestibility of meat. — Meat varies greatly in 
composition and digestibility. While man cannot digest 
stringy connective tissue and tough skin at all, yet good 
meat ranks next to milk arid eggs, and exceeds all forms 
of vegetable food in all the four points of digestibility. It 
requires a small outlay of time and energy in its digestion, 
and its oxidation develops a large amount of heat and 
energy. It does not easily ferment, and only about one 
thirtieth remains undigested. 

Meat is often salted or smoked or dried, or prepared in 
other ways so that germs of fermentation or decay will not 
grow in it, and thus it can be kept for a long time. When 
thus prepared, its fibers are partly coagulated and har- 
dened, so that the gastric juice cannot penetrate them 
readily. The digestibility of such meat is greatly impaired. 
The toughness of meat is due to strings of connective tis- 
sue, which are digested with difficulty and yield little heat 
and energy to the body. Tender meat consists almost 
wholly of muscular fibers, which are the main nutritive 
parts of most meat. Since meat contains no starch or sugar, 
some must be added in order to make it a perfect food ; 
and, very properly, bread is generally used. 



ANIMAL FOOD II5 

171. Soup and beef tea. — The water in which meat is cooked 
is often eaten as soup. Soup contains some gelatine and tat, but only 
a small amount of albumin, for most of the albumin is coagulated by the 
heat, and thus prevented from dissolving. The water also dissolves the 
mineral and waste matters of the meat. 

Beef juice is made by heating the meat and pressing out the juice. 
The best meat juice contains albumin and fat in about the same pro- 
portions as milk. 

Beef tea is a kind of concentrated soup. Mineral and waste matters 
give it flavor. It is very poor in albumin and fat, and is of little value 
as a food, while its waste matters may render it harmful. There are no 
facts to warrant the assertion that beef tea contains some nutritious 
essence of the meat which is of special value as food. Its value must 
be judged solely by the amount of albumin and fat which it contains. 
Extracts of meat are sold, a teaspoonful of which added to a cup of 
water is said to contain the nourishment of a pound of beef. They 
consist of mineral and waste matters dissolved in water, and so are of 
no value as food. Their taste may be pleasant, and this may assist in 
the digestion of other food. 

172. Fresh meat. — As a rule any meat is most whole- 
some if it is eaten soon after being killed. In the markets 
beef is usually hung in a room whose temperature is nearly 
freezing. There it remains fresh for weeks, or even months, 
and at the same time it becomes more tender and improves 
in flavor. When taken out and exposed for sale, it spoils 
much sooner than newly killed beef. If there is the slight- 
est musty or decayed odor about meat, it is undesirable as 
food. 

Game animals are often hung just as they are killed, 
until they are distinctly decayed, so as to develop pecuhar 
flavors. Fowl and game are liable to be unwholesome if they 
are kept for many days without being opened and cleaned. 

173. Points of good meat. — (i) Tender meat usually comes 
from well-fed animals, and such animals are always fat. A layer of fat 
from one fourth to one half inch in thickness, covering the outside of 
the meat just under the skin, usually denotes a well-fed animal. The 



Il6 APPLIED PHYSIOLOGY 

fat will also extend in fine white streaks irregularly in every direction 
through the meat and can be clearly seen upon its cut surface. 

(2) The fat is deposited in the connective tissue which incloses 
separate bundles of muscles. If these bundles are from one eighth to 
one fourth inch in diameter, and preserve their shape when the finger 
is passed over them, they contain much connective tissue, and the meat 
is tough, as in meat from the neck. When a slice of such meat is 
gently pulled apart, the bundles separate from each other, and are con- 
nected together by strong, veil-like meshes of connective tissue. 

On the other hand, if the bundles of muscle are small and not well 
marked, the connective tissue is small in amount. When a slice of such 
meat is pulled apart, its bundles do not separate, but the whole piece 
stretches. 

(3) The cut edge of good beef soon becomes bright red in color. 
When the connective tissue is abundant between the bundles, it im- 
parts a paler tint to the meat, and sometimes a bluish tinge. Good 
pork and veal are pale or almost white in color, but in other points 
resemble beef (see p. 218). 

Good meat has an agreeable odor and is clean. Excepting as 
it is marked by connective tissue and fat, it should be of a uniform 
tint. 

174. Fish. — Fish contains albumin about sixteen per 
cent, fat about six per cent. It is digested with rather less 
ease than meat, but it can take the place of meat as food. It 
used to be thought that it contained more nourishment for 
the brain than other kinds of food, but the brain is nour- 
ished by the same substances as the rest of the body, and 
fish is hardly so good for it as beefsteak. 

Fish should always be eaten while fresh, for it is espe- 
cially liable to decay. 

175. Shellfish. — Shellfish, as oysters and clams, contain 
about sixteen per cent of albumin and three per cent of fat. 
The large dark mass in their bodies is the liver, which con- 
tains some sugar. When eaten raw, their own digestive 
fluids and their livers aid in the digestion of their bodies. 
When cooked, they require more time and energy for their 



ANIMAL FOOD II7 

digestion. Because of their ease of digestion, fresh raw 
oysters are a vakiable food in sickness. Crabs and 
lobsters also are good food if well cooked. 

176. Blood. — Blood is digested with difficulty. It contains little 
albumin and fat and no sugar. It adds nothing to the value of meat, 
and is very liable to decay. It should always be removed, as is usually 
done in killing the animal. By the law of Moses the Jews were forbid- 
den to eat the meat of animals which had not been bled to death. 

177. Inferior meat. — Meat cannot be adulterated, but inferior 
meat is sometimes sold as good meat. Old meat is sold for fresh meat, 
and tough meat for tender. Very young animals are dangerous as food, 
and yet they are often sold. Meat from sick animals is always unfit for 
use. In France, horseflesh is sold for food under its own name, and in 
this country it is sometimes substituted for beef in cheap shops. 

178. Diseased meat. — Meat sometimes contains hving germs, 
which may produce disease in those who eat it. The most common 
disease to be feared is tuberculosis^ or consuifiption. Beef cattle are 
especially liable to have the disease, which may be located in their 
muscles as well as in any other part of their bodies, and is difficult of 
detection. 

A tape'wor)n passes one stage of its existence in the muscles of an 
animal. Its eggs are accidentally eaten by an animal, and develop into 
minute worms, which pass through the walls of the stomach into the 
muscles and there form white cavities about the size of a pin head, 
in w^hich they lie quietly. When flesh containing such a worm is 
eaten and digested by man, the worm is set free from its cavity, and, 
fastening itself to the inside of the intestine, grows to many feet in 
length. It lays eggs which will grow only when eaten by a lower 
animal. 

In pork there are sometimes found microscopic worms called tfichince. 
In the muscles of man they may grow and multiply enormously. The 
disease which they cause is both painful and deadly. It is extremely 
rare, at least in this country. 

179. Prevention of disease. — A sure preventive against any 
of these diseases is thorough cooking, for heat destroys all living germs. 
It has not been proved that salting and smoking meat kills the germs 
in it. There is no way of making musty or spoiled meat fit for food. 
Such meat never should be used. 



Il8 APPLIED PHYSIOLOGY 



SUMMARY 



1. Milk is the most easily digested and most perfect of 

foods. 

2. Hens' eggs contain an abundance of albumin and fat, 

but no starch or sugar. They are next to milk in 
ease of digestion. 

3. Next in order come meats, including fish and shellfish. 

4. Of meats, beef has high food value ; mutton, fowl, pork, 

game, fish, and shellfish rank next, in the order named. 

5. Animal food in general is easily and quickly digested 

and only about one twentieth remains undigested. 

6. Meat should be fresh and from a healthy animal. 

DEMONSTRATIONS 

52. Show samples of fresh milk and skim milk. Curdling of milk 
can be shown by adding vinegar to milk and gently stirring it until the 
curd collects in a lump. Show that this is cheese. By setting some 
milk aside in a deep bottle, the amount of cream which rises can be 
shown. Butter can be made from some cream, but the process is 
uncertain, especially in winter. 

53. Test some milk with a lactometer or a specific gravity bulb. In 
good milk it should sink to i .030. 

54. By cutting a hole in a piece of pasteboard and holding eggs in it 
in front of a lamp in a darkened room, contrast the bright pink of a 
fresh egg with the dull color of a state egg, as is done in testing eggs 
in the market. 

55. Show some fresh meat and some that is stale. Show some very 
tender and some very tough meat. Show that t]je toughness of meat 
is due to white strings of connective tissue. 

REVIEW TOPICS 

1. Give a definition oi food and tell what five substances 

are used for food. 

2. Show why an abundance of water is needed in food. 



ANIMAL FOOD 1 19 

3. Show why salt is the only mmeral which man adds to 

his food. 

4. Give the four points which determine the digestibility 

and value of a food. 

5. Show that milk is a perfect food and how it may be 

used to the best advantage, and how to avoid dis- 
eases which it may contain. 

6. Show how to distinguish good milk from poor, and 

describe two methods for testing it. 

7. Describe cheese. 

8. Describe butter and its imitations. 

9. Show how eggs are valuable as food and how they are 

deficient and how they had best be eaten. 

10. Show how a good ^g^ can be told from a spoiled one. 

11. Show how meat is valuable as food and how it is de- 

ficient. 

12. Compare beef tea with meat. 

13. Compare fresh meat with meat which has been kept 

and with decayed meat. 

14. Describe what diseases may be transmitted by meat, 

and how to avoid them. 

15. Show how to select good meat in the market. 

16. Show how fish and shellfish resemble meat. 



CHAPTER XIII 
VEGETABLE FOOD 

180. Grain. — Food prepared from grain contains 

Albumin .... 8 per cent to 1 5 per cent. 

Starch or sugar . . 50 " to 75 " 

Fat I *' to 10 

Mineral matter . . i " to 3 " 

Some forms of its starch or sugar are digested with a 
considerable expense of time and energy, and there is 
always a considerable portion left over. From grain 
nearly all the starch and sugar of food is obtained. 

181. Gluten. — The albumin of most grains is called 
gluten. It is easily dissolved in water and gives the 
sticky character to a mixture of flour and water. Its 
digestion requires an expenditure of more time and energy 
than the digestion of most forms of animal albumin, but 
its oxidation yields the same amount of energy. About 
one fifth is left undigested, whereas only one thirtieth of 
animal albumin is left. 

The husks of the kernels of grain and the cellulose frameworks 
within are wholly indigestible. When milk is digested, there is little 
waste matter upon which the intestine can contract. A food like grain, 
which leaves much waste matter, furnishes something upon which the 
intestine can contract, and thus sweep the waste matters on and out of 
the body. For this reason vegetable food is of use aside from its 
nutritive value. 

120 



VEGETABLE FOOD • 121 

182. Fermentation of grain in the alimentary canal. — 

Owing to its large amount of starch and sugar, and to its comparatively 
slow digestion, grain foods are liable to ferment. Fermentation will be 
the least apt to occur with a mixture of about equal parts of animal and 
vegetable food. 

183. Bread. — Bread is the most common form of food 
made from grain. Usually some means are employed to 
make the bread porous and soft. Yeast is commonly 
added. Its germs grow and change the sugar of the flour 
to carbonic acid gas and alcohol. The gas, bubbling 
through the wet and sticky flour, puffs it up and fills it 
with small cavities, whose form the stiff and sticky gluten 
preserves. Corn meal has but little gluten to make it 
sticky, and so it will not preserve enough porous character 
to form a loaf of bread. 

Instead of yeast, baking poivder is often used to make 
bread or biscuit light. The powder develops carbonic acid 
gas, which bubbles through the dough. Nearly all baking 
powders are minerals, and their use in large quantity is 
undesirable. 

Bread made from wheat flour requires less energy in its 
digestion than any other kind of vegetable food. Since 
some starch must be eaten, bread, in combination with 
milk, eggs, and meat, forms the best diet for everyday 
use. Rye flour makes nearly as good bread as wheat flour. 

184. Other forms of grain food. — Biscuit is bread with a 
little fat added and baked in small lumps. 

Cake is a mixture of flour, eggs, fat, and sugar. A large amount of 
fat or shortening \^n^% to make it indigestible. 

Pancakes are made of flour, corn meal, or buckwheat flour. If they 
are light and well cooked, they are of as much value as bread. 

Cracked wheat and other preparations of wheat are often boiled in 
water, forming a mush or pudding. This has the composition and 
digestibility of bread. 



122 ' APPLIED PHYSIOLOGY 

Corn meal boiled, or made into pancakes or corn breads is almost as 
easily digested as wheat flour. It contains a larger amount of fat than 
any other grain. 

Oatmeal when boiled to a mush is a very popular article of diet. It 
requires more time and energy in its digestion than any other common 
grain food. It leaves a large amount of undigested residue, which 
sweeps out other waste matters as it is forced down the intestine. 

Rice is poorer in albumin and richer in starch than any other grain. 
But when animal food is used in connection with it, there is no better 
combination of food, for it is the equal of flour in digestibility. 

Barley is but little used as food by man. It contains little albumin 
but a large amount of starch. 

185. Ways of preparing grain. — The finest grades of flour 

make bread which is digested with less cost of energy and with less 
residue than flour from the whole grain, while there is but little differ- 
ence in the amount of albumin and starch which they contain. Hot 
bread is injurious only when it is moist and sticky so that it cannot be 
chewed to fine morsels. Old bread is more easily digested than new 
because it is harder and drier, and so can be chewed fine. 

186. Beans and peas. — Beans and peas contain 

Albumin ..,,... about 25 per cent. 

Starch ''60 

Fat " 2 

Their albumin has much the same composition as the 
caseine of milk, and is called legumin. It requires a large 
expenditure of time and energy in its digestion. Both 
legumin and the starch are very liable to ferment in the 
intestine and produce gases. At least one fifth remains 
undigested. Beans and peas are good foods for an out- 
door laborer who has a great deal of spare energy. 

187. Potatoes. — Potatoes contain 

Albumin "... 3 per cent. 

Starch or sugar ....... 22 '* 

Water . 75 



VEGETABLE FOOD 1 23 

They are very poor in albumin, but rich in starch, so they 
go well with meat and eggs. Potatoes require a greater 
amount of time and energy in their digestion than bread 
and yield less heat and energy, and leave more undigested 
residue, and are more liable to ferment. 

188. Difference between animal and vegetable food. — 

Animal and vegetable foods differ in several particulars : 

First. Animal food requires less energy in its digestion. Animal, 
rather than vegetable, food is light diet. 

Second. Because of its longer time of digestion, and of the larger 
amount remaining undigested, vegetable food is more liable to ferment 
in the stomach and intestine, so that in severe sickness vegetable food 
is usually entirely withheld. 

Third. Vegetable food alone contains too much starch and sugar 
for the needs of the body. Fermentation is thus promoted. When 
absorbed, sugar is more readily oxidized than fat or albumin, and an 
excess of sugar takes oxygen from other parts of the body. 

189. special use of vegetable food. — While animal albu- 
mins and fats are more easily digested, and furnish a greater 
supply of heat and energy than the same kind of food of 
vegetable origin, it by no means follows that man should 
use them to the exclusion of vegetables. Their very ease 
and completeness of digestion may lead one to eat too 
much. Man's mouth and stomach combine the character- 
istics of herbivorous and carnivorous animals, and he will 
enjoy the best health when both classes of food are used. 
He must use some vegetable food for the sake of its starch 
or sugar. 

190. Effect of cooking. — The distinctions between food 
just given were based upon experiments made upon healthy 
men, who ate slowly, and masticated food properly cooked. 
All vegetable food should be cooked so that it is a dry and 
crumbly mass which the digestive juices can easily pene- 



124 APPLIED PHYSIOLOGY 

trate. Thorough cooking renders all kinds of food more 
digestible. Raw starch is indigestible. 

191. Green vegetables. — There are many kinds of vege- 
table food which supply little weight, heat, or energy to 
the body, yet are often eaten because of their agreeable 
taste. Beets, turnips, carrots, parsnips, pumpkins, and 
melons are poor in albumin. They contain some starch 
and sugar and much fibrous substance wholly indigestible. 
Their agreeable taste may increase the flow of the diges- 
tive fluids, and their bulk may excite the peristalsis of the 
intestine. 

Tomatoes, cabbage, cauliflower, onions, asparagus, and 
all other green vegetables are still poorer in food mate- 
rial, and are especially liable to ferment in the intestine. 

Green vegetables, such as cucumbers, which are eaten 
in an unripe state, are wholly indigestible. Thus they 
may pass through the intestine almost unchanged, or they 
may ferment and produce pain. 

192. Iron in vegetables. — Green vegetables contain a 
considerable quantity of iron-bearing albumin or nucleo- 
albicmin, while grain and animal food contain only a small 
quantity. This form of albumin is easily destroyed in the 
intestine if fermentation of food takes place. Under these 
circumstances green vegetables, by furnishing an abun- 
dance of this material, are a real food. Those should 
be chosen which do not readily ferment. Of them all, 
probably celery and spinach are best. 

193. Fruit. — Fruits, such as apples, pears, plums, 
peaches, and berries, have little albumin which man can 
digest, but often have a large amount of sugar. Their 
chief use is to fill the intestine when a food is eaten 
which, like milk, leaves but little undigested matter to sweep 
along with the bile and other waste matters. But all fruits 



VEGETABLE FOOD 1 25 

are liable to ferment in the intestine. Grapes contain 
more albumin than almost any other fruit, while their 
sugar is the form produced by digestion. For these 
reasons they are easily digested, and are a real food. 
Bananas also contain much albumin and sugar. Green 
fruit is digested with difficulty and is very liable to injure 
the stomach. Over-ripe and decayed fruits often contain 
poisons which produce violent sickness. Only a small 
quantity of any fruit should be eaten at once. 

194. Tart fruits. — Oranges, lemons, rhubarb, and such tart or 
sour articles of food are often said to be "cooling" to the blood. When 
the appetite fails, and the mouth is dry with a false thirst, their sourness 
excites the flow of the alkaline saliva, and so the mouth and tongue 
become moist, and the false thirst is relieved. In long voyages and 
expeditions, when fresh food cannot be obtained, they are of value in 
warding off scurvy. When eaten at meal times, the acid of sour fruits 
hinders the production of the gastric juice, and thus retards rather than 
aids digestion. In the stomach the acids unite with the mineral matters 
of the food, and then are absorbed into the blood. Their presence in 
the blood seems to have some eifect on the nutrition and action of the 
cells, and on this account they are sometimes given as medicine. They 
seldom take part in building up the body, but are quickly thrown off 
by the kidneys. The popular idea of their cooling effect is derived 
mainly from the fact that they excite the flow of saliva, and thus render 
the mouth moist. 

195. Nuts. — Nuts contain oil, but it is doubtful if much 
of it is emulsified and absorbed. They contain an abun- 
dance of albumin and starch, but their digestion usually 
requires more time and energy than the stomach of man 
is designed to furnish. 

196. Canned food. — When food is heated so as to destroy its 
living germs, and then is at once sealed air-tight, it will neither decay 
nor sour, and when opened a long time afterwards it will be found to be 
as fresh and wholesome as when it was put into the can. Thus it is 
possible to carry fresh meat and vegetables on long voyages or to remote 



126 APPLIED PHYSIOLOGY 

and cold countries. When carefully prepared, canned food is as whole- 
some as food recently cooked. When opened it soon spoils. 

197. Scurvy. — When men have been living for months 
upon bread and salt meat, without fresh food, there some- 
times comes a disease called scicrvy. The gums become 
sore, and the legs ache and turn ''black and blue'' as 
though they were bruised. Then fruit or green vegeta- 
bles are of the highest value, probably because they fur- 
nish a good supply of mccleo-albumin, in which old bread 
and salt meat are apt to be deficient. 

198. Seasonings. — Pepper, mustard, nutmegs, cloves, and all such 
sharp- tasting things are added to food simply for their taste. They are 
probably neither digested nor oxidized, and yield neither weight, nor 
heat, nor energy. They irritate and burn the stomach just as they do 
the mouth. Yet their pleasant taste may be of value in promoting the 
flow of the digestive juices. 

199. Tea and coffee. — Tea and coffee are often sup- 
posed to supply food to the body. They belong to the 
class of substances which, acting through the nervous 
system, spur on the work of the cells of the body, espe- 
cially of the brain. They supply no heat or energy for 
the extra exertion. Substances which excite the cells to 
action, without giving them material out of which to 
develop heat and energy, are stimulants. The active 
principle of tea and coffee is a stimulating substance 
called caffeine which spurs the cells of the body to do 
more work. They enable a person to do a larger amount 
of work in an emergency, and when the body is tired they 
rouse the digestive and assimilative organs to renewed 
activity, so that these quickly prepare a new supply of 
food. When they are used continually the body learns to 
rely upon their stimulation. Thus a habit of drinking them 
is formed which is not easily broken. 



VEGETABLE FOOD 12/ 

200. Tannin. — Coffee and tea also contain some tan- 
nin, which is a substance used in the manufacture of 
leather. It puckers and contracts albumin with which 
it comes in contact, and is liable to hinder digestion. 
Much of the bad effect of strong tea is due to its tannin. 

201. Volatile oils. — Both tea and coffee also contain a 
considerable quantity of an oil, which gives the drinks their 
pecuHar odors and flavors, but which evaporates quickly. 
It is mainly this oil which produces headache and sleep- 
lessness and other troubles, when large quantities of tea or 
coffee are taken. Yet both drinks agree with the stomach 
better when the oil is retained in the drink. 

202. Preparation of tea and coffee. — Both the caffeine and 

the oil of tea and coffee are easily dissolved by boiling water, but by 
long boiHng the volatile oil is driven off in the vapor, and a large 
amount of tannin is extracted. Both these results are undesirable, and 
can be avoided by pouring boiling water over the tea and coffee, and 
then steeping it slowly for only a few minutes. 

Coffee will be digested more easily if the milk which is added is 
boiled with the coffee. Better still would be to add no milk at all. 

203. Adulteration of tea and coffee. — it is easy to add the 

leaves of other plants to tea leaves. Green teas are often colored with 
copper. 

Coffee is adulterated with all kinds of roasted roots. A root called 
chicory is cultivated especially for this purpose. 

204. Cocoa. — Cocoa contains a small quantity of a sub- 
stance which stimulates like caffeine. It also contains a 
considerable quantity of albumin and fat, both of which 
will dissolve in water. Thus it is more of a food than tea 
or coffee, and its use is less likely to cause indigestion. 
Chocolate is a preparation of cocoa. 

205. Use of tea and coffee. — Tea and coffee are not 
necessities, and men would be just as healthy without 
their use. They have a reputation of retarding waste 



128 APPLIED PHYSIOLOGY 

of the body, but this view is not founded upon definite 
experiments. The nervous system of children is easily 
impressed by tea and coffee, and their bodies cannot stand 
the stimulation and extra work which these substances 
induce. When long and fatiguing work mnst be done or 
great exposure endured, then tea and coffee are valuable 
stimulants. 

206. Adaptation of man's stomach to certain foods. — 
Green vegetables, fruit, and grass contain the proper 
quantities of food elements to support man's life, but 
man cannot digest them readily. Lower animals eat the 
food and expend their digestive energies on it ; finally, 
when man eats it in the form of milk, eggs, or meat, it 
needs but little further digestion. 

SUMMARY 

1. Grain is the main source of vegetable food. 

2. Grain albumin, or gluten, is digested at more expense 

of time and energy than the albumin of animal food. 

3. Grain food contains much starch, and must be eaten 

to supply this element. 

4. Grain food is more liable to ferment than animal food. 

5. Bread is the form of grain most available for digestion. 

6. Boiled preparations of grain contain the same food 

elements as bread. 

7. The most valuable of the grains which are usually 

eaten boiled are rice, cracked wheat, corn meal, and 
oatmeal. 

8. Cake and biscuit may be considered as forms of bread. 

9. Beans and peas are rich in albumin and starch, but 

require a great deal of energy in their digestion. 
10. Potatoes are poor in albumin but rich in starch. Their 
digestion requires much energy. 



VEGETABLE FOOD I 29 

11. Animal food in general fulfills the points of digestibil- 

ity better than vegetable food. 

12. Green vegetables and fruit are of value because their 

taste may excite the flow of digestive fluids ; the 
large residue left after their digestion may sweep 
waste matters down the intestine ; and they may 
form a supply of nucleo-albumin when the supply 
in ordinary food is deficient. 

13. Green vegetables and fruit should be eaten a little at 

a time, because of their great liability to undergo 
fermentation. 

14. Tea, coffee, and cocoa spur the cells on to renewed 

activity when the body is tired or weakened. 

DEMONSTRATIONS 

56. Grain albumin, or gluten, can be separated by mixing a small 
mass of dough of wheat flour and gently washing out the starch by 
kneading it under water. The gluten will be left as a stringy, sticky 
mass. The starch in grain can be shown by the iodine test (page 31). 

57. Show samples of bread, both light and heavy, sweet and sour, 
well-baked and under-done, new and stale, and hot and cold. Show 
that the difference between the last three pairs depends upon the one 
kind forming a pasty mass when wet or chewed, while the other kind 
may be broken into fine particles. 

58. Show samples of properly cooked and of improperly cooked 
rice, oatmeal, etc. 



REVIEW TOPICS 

Give the composition of grain. 
Describe the albumin of grain. 
Describe bread and the process of its manufacture. 
Describe foods which are Hke bread. 
Describe the various kinds of grain which are eaten 
when boiled to a mush. 

OV. PHYSIOL. — 9 



130 APPLIED PHYSIOLOGY 

6. Give the difference of digestibility between bread 

made from unbolted and fine flour; between hot 
and cold bread ; between new and old bread. 

7. Give a reason why grain food should not be sweetened. 

8. Describe beans a.nd peas. 

9. Describe potatoes. 

10. State why the method of cooking and the manner of 

eating make a great difference in the value of 
vegetable foods. 

11. Give the main points of difference between animal 

and vegetable foods. 

12. Name the food elements in green vegetables and in 

fruits. 

13. Give the important uses of green vegetables and fruits. 

14. Tell how green vegetables and fruits should be eaten. 

15. Show that man's stomach is adapted to certain kinds 

of food only, and tell how all kinds of food may 
ultimately become adapted to his use. 

16. Give the active principles of tea, coffee, and cocoa, 

and the effects of each upon the body. 

17. Name the food elements in milk; in eggs; in meat; 

in grain ; in potatoes ; in beans. 

18. Give the organ in which each of the following foods 

are acted upon, the digestive fluids which act upon 
it, and the chemical change produced by each fluid: 
milk, eggs, meat, bread, butter, grain food, potatoes, 
beans. 



CHAPTER XIV 
QUANTITY OF FOOD REQUIRED 

207. Amount of food elements required. — Although 
oxidation is continually going on in each cell of the body, 
only a small part of the albumin eaten is required in their 
reconstruction ; the remainder and all the sugar and fat 
are oxidized without ever becoming a part of the living 
cells of the body. 

In order to repair the waste caused by the oxidation of 
the cells, and to supply the requisite amount of heat and 
energy, the average man must assimilate daily — 

Albumin 4^ ounces 

Fat 4 

Sugar or starch 5 " 

208. Amount of oxygen required. — The amount of oxy- 
gen needed to oxidize the — 

Albumin is ij times its own weight, or 6.3 ounces 
Fat 3 " " " 12 

Sugar jl " '' '' 6 

Total amount of oxygen required daily, 24.3 ounces 

The average amount of oxygen taken in daily by the lungs 
is twenty-four ounces. When more food is eaten than this 
amount of oxygen can oxidize, some of the albumin is 
changed to fat, which increases the weight of the body. 
Anything which causes the lungs to take in more oxygen 

131 



132 



APPLIED PHYSIOLOGY 



will enable the body to oxidize more food. So the laborer 
breathing deeply of fresh air is less troubled with the bad 
effects of over-eating than a clerk in an office. 

209. Oxidation of an excess of sugar. — Sugar is more 
rapidly oxidized than other food, and when too large a 
proportion of starch or sugar is eaten the other food is 
incompletely oxidized, and sickness is the result. A 
greater proportion of starch is required when more heat 
and energy are needed, as in physical labor. 

210. Selection of diet. — To supply the proper elements, 
a variety of food may be selected, of which the following 
diet for twenty-four hours is a typical example. 





Oz. OF 

Albumin. 


Oz. OF 

Fat. 


Oz. OF 

Sugar. 


7 ounces of bread contains . . . 

3-5 " eggs (2) " ... 
14 " meat " ... 
24 " milk(i|pt.)" . . . 

1.5 " butter " ... 


0.7 
0.5 

2.5 
0.9 





2 

1-5 


4.2 





1.2 




Total 


4.6 


5 


54 



Allowing for the amount usually left undigested, there 
would remain about the proper amount of each kind of 
food element. This food contains more than enough min- 
eral matter to supply all the needs of the body. 

211. Choice of food. — The price of food has little to do 
with its nourishing qualities. Fine taste, good appearance, 
and rarity are usually what make foods costly. The 
cheaper kinds are quite as nourishing as the more fashion- 
able, and will taste as good if they are well cooked. About 
three fourths of a laborer's wages are spent for food. 
Cheaper meats and fish, with less sugar and desserts, will 



QUANTITY OF FOOD REQUIRED 1 33 

furnish him a better diet, and at less cost. It is as bad 
economy for a poor man to buy the best of food as it is for 
him to buy silk and broadcloth clothing. Scraps and food 
left over from the table are as good quality as ever, and 
should be saved for the next meal. 

212. Amount at a meal. — Rules prescribing the amount 
of food to be eaten at once cannot be given, any more 
than fixed rules regulating the amount of wood to be 
added to the fire in a cooking stove. Hunger and taste 
are reliable guides when plain food is eaten slowly. 

213. Too much food. — In some persons the stomach cannot 
digest and absorb food so fast as the lungs can furnish oxygen for its 
oxidation. While these persons eat heartily they generally remain 
thin, for, instead of accumulating food, they use it up in developing 
energy for active work. They are apt to overwork their stomachs and to 
suffer from indigestion. They need nutritious and easily digested food. 
Other persons can digest food faster than the lungs can supply oxygen 
for its oxidation. These persons eat little, but, since the slow oxidation 
allows food to accumulate, they are apt to be fat and lazy and to suffer 
from lung troubles. By allowing their strong stomachs to act upon the 
less easily digested foods their appetites wall probably be satisfied, and 
still not enough food will be digested and absorbed to overtax their lungs. 

214. Starvation. — When man is deprived of all food, life 
is supported by the oxidation of his own flesh as long as it 
lasts. In from six to ten days a man will lose two fifths 
of his original weight, and then death occurs. When water 
is given, Hfe will last for a much longer time. 

215. Brain food. — Brain workers require the same kind of food 
as the laborer. In its action the brain uses heat and energy, the same 
as any other part of the body. Fish is no more a brain food than beef- 
steak. Phosphates, which are popularly supposed to nourish the brain, 
are arrested at the liver ; but they stimulate the liver to greater activity, 
so that food is more perfectly assimilated, and thus greater strength is 
given to the brain cells, as well as to the rest of the body. Phosphorus 
is found in most foods in greater quantities than the body needs. 



134 APPLIED PHYSIOLOGY 

SUMMARY 

1. About four ounces of each of the food elements — 

albumin, fat, and sugar — must be eaten daily. 

2. To oxidize this amount of food requires about twenty- 

four ounces of oxygen, which is about the amount 
breathed in. 

3. A diet of bread, eggs, meat, milk, and butter will fur- 

nish the best food elements. 

4. If too much sugar or starch is eaten, the albumin and 

fat are not fully oxidized. 

5. If too much food is eaten, all the oxygen is used up, 

and there is none left for an extra exertion. 

6. If little or no food is eaten, not enough heat and energy 

are produced to keep the body alive. 

DEMONSTRATIONS 

59. Weigh out the dififerent amounts of bread, eggs, meat, milk, and 
butter which are required daily. Also measure out a quart of water. 
This will show the class the amounts of food required daily. 

60. Weigh out the required quantities of albumin, fat, and sugar. 
Albumin may be represented by gelatine or glue. 

REVIEW TOPICS 

1. Give the amount of albumin, fat, and sugar required 

daily. 

2. Give the amount of oxygen required to oxidize the food. 

3. Give the results of oxidizing an excess of sugar. 

4. Give the amounts of bread, meat, etc., required daily to 

furnish the body with the proper amount of albumin, 
fat, and sugar. 

5. Give the best times for eating. 

6. Give the effects of eating too much food ; of too little. 



CHAPTER XV 

DRINKING WATER 

216. Pure water. — Water is the only food which man 
habitually takes without its previous preparation. Water 
is the same from whatever source, but substances dissolved 
in the water change its appearance. Carbonic acid gas, 
oxygen, and air are dissolved in all ordinary water, and in 
it float particles of dust and harmless living germs. Such 
water is clear and colorless. It has a slight taste, due to 
the dissolved air. When the air is expelled by boiling, the 
water is insipid and almost tasteless. 

217. Hard and soft water. — Water also contains a vari- 
able amount of mineral matter, especially lime, soda, and 
potash. Water containing lime makes the fingers feel 
slightly rough and puckered. The lime combines with 
soap, forming a scum which will not dissolve. Water con- 
taining lime is said to be hard, while water with little or no 
lime is soft. Although some gases and minerals are dis- 
solved in all water, they are harmless and do not make it 
impure, but rather they give it a more pleasant taste. 
When very hard water is boiled, some of the lime is 
deposited on the sides of the kettle, and the water is 
improved but not made soft. 

218. Mineral waters. — When much mineral matter is present 
the water is called minej-al water. The principal minerals thus found 
in water are salt. lime. soda, potash, iron, and sulphur. These waters 
form springs in various parts of the country, and have borne a great 

U5 



136 APPLIED PHYSIOLOGY 

reputation as healing agents even among the Indians. Enormous 
quantities are sold for drinking and medicinal purposes. Some contain 
one or two ounces of mineral substance to each gallon of water. Some 
springs contain almost pure salt, and furnish the greater part of the 
table salt in common use. 

219. Impure water. — When water contains substances 
which are directly injurious to health, it is impure. Water 
which stands in lead pipes may slowly dissolve some of the 
lead, but if the water is allowed to flow, the dissolved lead 
will be washed away. Water from muddy or stagnant 
streams is of a bitter taste and unpleasant odor and turbid 
in appearance, so that it is not likely that it should be used 
as a drink; but well water often becomes polluted with 
poisons far more injurious than those developed in stag- 
nant streams, and the danger is all the greater because 
it often remains clear and sparkling and pleasant to the 
taste. 

220. Decayed matters and disease germs. — The danger- 
ous substances most often found in water are decaying 
matter and disease germs. While decaying matter is 
itself poisonous, yet its greatest danger lies in the fact 
that it forms the food upon which living germs of disease 
can live. These are ready to grow when taken into the 
body. Typhoid fever is almost always transmitted in this 
way. In pure water germs soon die of starvation, but 
they grow readily if a small amount of decaying matter 
is present. Water which is colored or has an odor or a 
taste is almost sure to contain decaying matter, which may 
become a breeding place for the germs. Such water 
should be avoided; but water which is clear and sparkling 
may still contain food for the germs. 

221. Source of impurities. — Sewage and slops from a 
person suffering with an infectious illness may contain 



DRINKING WATER 1 37 

germs of the disease. These germs may grow in the 
slops after they have been emptied. If these slops find 
their way into a well, the disease germs may continue 
to grow and may infect any one who drinks the water. Ice 
from such water may also contain the germs. A shallow 
well near any source of dirty water may become infected 
and so be a center for the spread of disease. 

222. Purification by oxidation in the soil. — The ground 

has the power of oxidizing decayed vegetable and animal matter so 
that only the mineral parts remain. Slops from the house are thus 
oxidized, if the ground is not soaked through with them. But when 
the quantity is great, some may work their way through the ground for 
a considerable distance and finally enter the well. 

223. Purification by filtration. — Clean sand has the power to 
screen out particles carried by the water. Screening out substances 
from water by passing it through a powdered substance is called yf//r<rz- 
tion. As the slops slowly soak through the soil, their solid parts are 
filtered out in the first few inches of the top soil, and if the quantity is 
not too great, are soon oxidized. Soils differ in their ability to filter. 
Clean sand is the best ; clay is the poorest. It is almost impossible to 
saturate sandy soil about a single house so that decaying matter can 
reach the Avells ; but in villages and cities the soil is so completely 
soaked that the well water of these places is impure ; and at any time 
germs may enter the polluted wells and grow. 

224. Purification by running water. — The third way in 
which water is purified is by the action of the air and sun upon running 
water. Sewage from the" towns is conducted into rivers, and the sun- 
light and agitation of the waters soon cause the waste matters and 
germs to be oxidized. 

225. Purification by boiling. — It is dangerous to use 
impure water for washing, for germs may remain upon 
the things washed. Typhoid fever has been spread by 
milk cans which were washed in water from a polluted 
well. A ready safeguard against the greater dangers of im- 
pure water is boiling, which destroys the germs of disease. 



138 APPLIED PHYSIOLOGY 

SUMMARY 

1. Water containing lime is hard, but without lime it is 

soft. Lime seldom injures water for drinking pur- 
poses. 

2. When other minerals, such as sulphur, iron, soda, or 

potash, are present, water is called mineral water. 
Such water is used as medicine. 

3. Air dissolved in water gives it a pleasant taste. 

4. Water containing decaying matter is poisonous. 

5. The greatest danger from impure water lies in the 

germs of disease which it may contain. 

6. Boiling the water is the best safeguard against impure 

water. 

7. The soil purifies water by oxidizing and filtering the 

impurities. Running water is generally pure. 

DEMONSTRATIONS 

61 . Show that all water contains mineral matter by evaporating a 
few drops of pure spring water upon a piece of clean glass. A little 
white spot will be left by each drop. Boil some water and notice the 
absence of taste. Cool it and shake it in a can, and notice its natural 
taste again. Set aside some pure water containing a few bread crumbs 
or a shred of meat, and notice the unpleasant odor of decay developed 
in a few days. 

62. A rough test for the purity of water is to stir in a little pure 
sugar and set it aside. If it contains any organic matter, it will turn 
yellowish in a few days, but otherwise it will remain colorless. Collect 
some rain water from a dirty building, or mud-puddle water, or water 
from a barnyard well, and note the color and the odor. After keeping 
it a few days, note the deepened color and worse odors, showing decay 
within the water. 

63. Doubtless the class will ask to be shown " animalculae " in 
water. Water has to be almost turbid and putrid before living beings 
are present in sufficient numbers to be easily detected with a micro- 



DRINKING WATER I 39 

scope. If a drop of very stagnant water is examined under the micro- 
scope with a power of 100 to 400 diameters, many strange beings will 
be seen moving about. Place a little hay in a bottle of water and exam- 
ine a drop of the water every day, and notice the changing forms of the 
living beings as one kind dies and another is produced. 

REVIEW TOPICS 

1. Describe the appearance and taste of pure water. 

2. State what substances are found in all water ; what in 

mineral water ; and the difference between Jiard and 
soft water. 

3. State the two common dangerous impurities of water. 

4. Give three ways in which nature purifies water. 

5. Show how to avoid pollution of a well. 

6. Show how to render impure water safe for use. 



CHAPTER XVI 
NARCOTICS 

226. What man eats besides food. — Besides eating food 
and harmless things which please the taste, man also eats 
a variety of dangerous substances, both for pleasure and 
to overcome some real or fancied weakness of the body. 
The physician prescribes them to overcome diseases of 
the cellS; but thoughtless and ignorant people use them on 
their own responsibility, and suffer great harm thereby. 
They may be divided into narcotics, drugs , and poisons. 

227. Narcotics. — There is a class of drugs which be- 
numb the sense of pain and fatigue and lessen the action 
and strength of the cells of the body. These drugs are 
called narcotics. They all are powerful poisons. They 
lessen the sense of effort and of fatigue, and are often 
supposed to be stimulants. A peculiarity common to all 
is, that when their benumbing effects have passed off, the 
real weakness of the body becomes doubly apparent, and 
there is an overwhelming desire for more of the drug to 
benumb the increased weakness caused by the first dose. 
Thus enslaving habits are formed. 

228. Alcohol as a narcotic. — Alcohol should be classed as 
a narcotic drug. It really belongs to the class of stimulants as well. 
A small amount acts as a stimulant ; but a large amount overwhelms 
the body and produces an insensibility to pain and fatigue, a dullness of 
mind, and a deep sleep. The use of alcohol tends to become a fixed 
habit, as is the case with other narcotics. 

140 



NARCOTICS 141 

229. Alcoholic poisoning. — Besides slow poisoning, alco- 
hol can produce severe poisonous effects at once. A man 
" dead drunk " is poisoned by alcohol, and is in danger of 
his life. In treating him, vomiting should be induced as 
soon as possible. He should be rubbed to keep up the 
circulation, and stimulated with hot coffee. Keep his 
body, and especially his feet, warm. 

230. Tobacco and nicotine. — The essential part of tobacco 
is a strong narcotic poison called nicotine. Pure nicotine 
is a clear and colorless liquid. It can be turned to vapor, 
and is found in the smoke when the tobacco is burned. It 
is a powerful poison, producing stomach sickness and great 
weakness of all the cells of the body, especially of the 
heart. Two or three drops will kill a man. 

231. Effects of its continuous use. — When used continu- 
ously, the body becomes somewhat accustomed to nicotine, 
so that it does not produce so great a feeling of sickness. 
Then instead of producing a feeling of w^eakness, it acts 
more to benumb the cells and to quiet the body. This is 
really the first stage of poisoning, although it seems like a 
stimulation. If a little more tobacco than usual is used, 
the benumbed and pleasant feeling changes to one of sick- 
ness, as though it were being used for the first time. It 
always continues to have bad effects upon the muscles, 
heart, lungs, eyes, and brain. Tobacco is especially inju- 
rious to young persons, hindering their growth and lessen- 
ing their strength. 

232. How tobacco is used. — Tobacco is used in smoking, 
in chewing, and in snuffing it up the nose. 

233. Smoking. — Tobacco is smoked in a pipe or by 
lighting the end of a roll called a cigar. Some of the 
nicotine is turned to vapor and enters the mouth, where 
it may be absorbed. Some of the nicotine is half burned, 



142 APPLIED PHYSIOLOGY 

and forms a substance called pyridine, which is even more 
poisonous than nicotine. In a cigar the burning is more 
complete, and less pyridine is formed. Cigarettes are small 
cigars made of shredded tobacco. They are cheap and 
may be quickly smoked, and are less liable to produce imme- 
diate sickness than a cigar. So the young are especially 
apt to use them. But they are commonly used to excess, 
and so make up in quantity of poison what they lack in 
quality. 

234. Chewing. — Chewing tobacco is the most harmful 
form of its use, for all the nicotine is taken into the mouth. 
Few people can chew tobacco without spitting out the 
saliva which contains the nicotine. The continuous spit- 
ting which is necessary to get rid of the saliva makes this 
form of using tobacco offensive to everybody near the 
chewer. This reason alone should deter any one from the 
practice of chewing tobacco. 

235. Snuff. — Snuff is powdered tobacco. A hundred 
years ago it was fashionable for women, as well as men, 
to use snuff. Now a snuffbox is a rare curiosity. 

236. Adulteration of tobacco. — The nicotine from stalks and 
remnants is extracted by boiling, and the liquor is used to saturate poor 
tobacco and the leaves of other plants. 

Chequing tobacco owes much of its taste to rum, molasses, licorice, 
and other things with which it is flavored. 

Most cigarettes are flavored with drugs which color the fingers of 
the smokers. Cigarettes are harmful enough at best, but the harm is 
far greater when they contain opium. Probably a great part of the 
craving which cigarettes induce is caused by the opium. 

237. Tobacco habit. — Like all other narcotics, when it 
is used for a short time tobacco produces a- persistent crav- 
ing. Men laugh at the idea of being slaves to such a 
small thing as smoking or chewing, and yet when the habit 



NARCOTICS 143 

is interrupted, there follows a peculiar unsatisfied and 
nervous feeling which few men are able to overcome. 

Alcohol and tobacco often go hand in hand. Tobacco produces a 
dr)' state of the mouth which demands drink, while alcohol causes a 
nervous excitement which the benumbing tobacco tends to overcome. 
Most users of alcohol smoke. The only way to break off the habit of 
using tobacco is to do so by resolute efforts of the will. So-called cures 
of the habit are of no value, for they cannot give a man a strong will. 
On the other hand, they may induce sickness. 

238. Tobacco poisoning. — Severe tobacco poisoning is 
rare ; for when swallowed or inhaled, it produces vomiting, 
which expels the poison. When applied to the skin in the 
form of a poultice, as is sometimes done, enough may be 
absorbed to produce great weakness, for then the stomach 
cannot expel it. The principal sign of poisoning is extreme 
weakness of the muscles and heart. 

To treat it, strong coffee should be given, and the patient 
should be kept perfectly at rest. 

239. Opium. — Opium is a narcotic drug which is used 
to benumb the feelings of fatigue and care. A little of the 
drug acts partly as a real stimulant, causing the cells to 
act more vigorously and clearly. At the same time its 
benumbing action is beginning, and only a little more is 
needed to produce a drowsy feeling or a deep sleep. Just 
as it causes the brain cells to cease acting in sleep, so also 
it lessens the action of all the other cells, and especially 
of those of the alimentary canal. The disturbance in the 
action of the intestine sets up digestive trouble, which 
extends rapidly to the liver. Then the nutrition of the 
whole body is lowered. No habit is more enslaving or 
more harmful in its effects. 

240. Cure of the opium habit. — The only cure for the 
opium habit, and yet a safe -and sure one, is to keep the 



144 APPLIED PHYSIOLOGY 

patient entirely away from the drug for a few weeks, con- 
fining him if necessary. After a short time the craving 
disappears and the patient recovers his health. 

241. Opium poisoning. — A lump of opium the size of a 
small pea, and weighing about two grains, is enough to put 
a man into a deep sleep. Twice that amount may cause 
death. When a person takes an overdose he falls into a 
deep sleep, from which he can be awakened only with 
difficulty. He breathes very slowly, and distends the 
lungs very slightly. The pupils of his eyes contract to 
small points. These three signs nearly always mean 
opium poisoning. They should be remembered, for this 
is the most common form of poisoning. 

242. Treatment of opium poisoning. — First. Keep the 
patient awake by such vigorous measures as slapping his 
face, shaking his body, and compelling him to walk. 

Second. Induce vomiting. A tablespoonful of mustard 
in water should be given at once if the person can swallow. 
Tickling the throat with the finger or a feather will gener- 
ally cause vomiting. 

Third. Stimulate the patient with strong, hot coffee. 
Carry out these measures slowly and deliberately. 

243. Forms of opium. — Opium is the dried juice of a kind of 
poppy plant growing in Southern Asia. Laudammi is opium dissolved 
in ten parts of alcohol. Paj-egoric is a more dilute solution of opium. 
A teaspoonful of it contains one quarter of a grain of opium. About 
one tenth of opium is a white substance called morphine. One quarter 
of a grain of morphine will cause a deep sleep and contracted pupils 
like a large dose of opium. 

244. Use of opium. — Opium is used to quiet pain, pro- 
duce sleep, and to quiet the intestine. 

Paregoric is sometimes used to quiet babies when they 
cry. It produces indigestion and leaves the child worse 



NARCOTICS 145 

than before. "Soothing sirups" are nearly always some 
preparation of opium. 

245. Chloral. — Chloral is a colorless solid, having a 
peppery odor and taste. About twenty grains will produce 
sleep, but an overdose may produce death. It injures the 
digestive organs and weakens the whole body. It is a 
narcotic and a poison. 

246. Chloral poisoning. — In treating a case of chloral 
poisoning the patient should be kept awake by walking 
him about, or even by slapping him. Give a tablespoon- 
ful of mustard in water to make him vomit. Then give 
strong coffee to stimulate him. 

247. Cocaine. — Cocaine is a drug which, when injected 
under the skin or applied to a mucous membrane, takes 
away the sense of feeling of the part. A grain of it will 
render a large area so completely insensitive for half an 
hour that large operations can be performed without sense 
of pain. It may cause excitement like the beginning of 
a state of drunkenness ; sometimes it produces great weak- 
ness of the heart and death. 

The excitement caused by the drug is pleasant, and per- 
sons can acquire a slavish habit of its use. It rapidly dis- 
turbs digestion and nutrition, and soon causes death. It 
is one of the most rapid and terrible forms of habitual drug- 
taking. 

248. Hasheesh. — Hasheesh is the juice of the Indian 
hemp plant, and is sold as a medicine under the name of 
cannabis indica. In Southern Asia it is extensively used 
as a narcotic. It produces a happy delirium, in which 
a person sees most beautiful persons and figures. The 
state is really a temporary insanity, in which one is liable 
to injure others. The word "assassin" means one under 
the influence of hasheesh. 

OV. FHYSIOL. — 10 



T46 APPLTED PHYSIOLOGY 

249. Chloroform. — Chloroform is a sweet-smelling liquid 
which, when breathed into the lungs,. causes a deep sleep. 
It is used to produce insensibility during surgical opera- 
tions. Its use requires extreme care, for it can easily 
result in death. No one should even smell a bottle con- 
taining it, for two or three breaths of it may render a per- 
son insensible. 

SUMMARY 

1. Narcotics lessen the sense of fatigue and pain and 

produce sleep, but weaken the body and may cause 
death. Their use may become an uncontrollable 
habit. 

2. Alcohol is a kind of narcotic. 

3. Tobacco contains the narcotic nicotine. A little nico- 

tine quiets the cells, while more causes weakness, 
and stomach sickness which may result in death. 

4. Tobacco used in any form produces poisonous effects. 

5. The tobacco habit tends to the use of strong drink. 

6. Opium quiets the cells of the body, lessens the sense 

of pain, and produces sleep. A little causes a feeling 

of exhilaration, while a few grains may cause death. 
The opium habit deranges digestion and finally causes 

death. 
In poisoning by opium there are a deep sleep and 

contracted pupils and slow breathing. 
The poisoned person should be kept awake, made to 

vomit, and stimulated by coffee. 
10. Laudanum, paregoric, and soothing sirups are all 

forms of opium. 
Chloral produces sleep. A large dose may cause 

death. Treat its poisoning like opium poisoning. 
12. Chloroform, when inhaled, produces insensibility. 



NARCOTICS , 147 

REVIEW TOPICS 

1. Define and describe narcotics and show how their use 

may become a habit. 

2. Show that alcohol is a narcotic, and give the signs 

and treatment of its poisonous effects. 

3. Describe the poison of tobacco and its effects. 

4. Describe the harm resulting from the use of the several 

forms of tobacco. 

5. Show the fraud and harm of adulterating tobacco. 

6. Show that the use of tobacco and alcohol naturally go 

together. 

7. Describe the effects of opium and the opium habit. 

8. Describe the signs and treatment of opium poisoning. 

9. Name some common forms of opium and give their 

uses. 

10. Describe chloral, and give the signs and treatment of 

poisoning by it. 

11. Describe cocaine, its use in surgery, and its poisonous 

effects. 

12. Describe hasJieesJi. 

13. Describe cJilorofoi-m and the danger of its use. 



CHAPTER XVII 
DRUGS AND POISONS 

250. Nature of disease. — Disease is due to some de- 
rangement of the action of the cells of the body. The 
derangement is almost always produced by overwork of 
some kind, for the cells are able to protect the body 
against all ordinary causes of disease. Few people who 
are exposed to epidemic diseases take them, because the 
cells are able to destroy the germs as fast as they enter 
the body. If men would eat, breathe, and in all things 
live as physiology and hygiene show that nature intended 
them to live, the cells would be strong enough to resist 
almost any disease. 

251. Action of drugs. — Each drug has a special influ- 
ence upon certain cells of the body, and is able either to 
stimulate or to restrain their action. Under the influence 
of the proper drug, each deranged cell takes in nourishment 
and performs its duties more perfectly, and soon overcomes 
the sickness. Thus the cells themselves, and not the drug, 
cure the disease. 

252. Action of a few common drugs. — When the liver is 

deranged, calomel or podophyllin will usually stimulate it to action. In 
stomach indigestion imtriatic acid and pepsin supply the missing diges- 
tive agents. When the heart is weak, digitalis or stjycJmine cause it 
to act more strongly, while if it is excited, aconite will quiet it. A fever 
is often lowered by aconite or phenacetine . When there is pain, opium 
will generally relieve it. When the brain is excited and the person is 

148 



DRUGS AND POISONS 1 49 

nervous or delirious, chloral or bromide of potash will quiet the cells. 
These are a few examples of the actions of drugs which physicians 
prescribe. 

253. Quack medicines. — Drugs should never be given except 
by a physician. The country is flooded with medicines advertised to 
cure various diseases. People who take them generally get well, but 
they forget that the cells of the body themselves tend to overcome all 
diseases, and that in all probability they had no disease at all, but were 
only feeling bad because of improper eating, or of overwork. 

254. Poisons. — All narcotics and drugs are poisons and 
cause sickness or death when taken in overdoses. The 
signs of poisoning are much alike in all cases. A person 
previously well suddenly feels very sick and weak, or be- 
comes unconscious. Vomiting often occurs, and pain is 
often present. 

255. Treatment of poisoning. — The first thing to do 
whenever a poison is swallowed is to empty the stomach 
as quickly as possible. Almost anybody can be made to 
vomit by tickling the throat with a finger, or with a feather 
passed through the nose if the mouth cannot be opened. 
A tablespoonful of mustard in a cup of warm water will 
generally cause vomiting and is always safe. A teaspoon- 
ful of alum in water will act in the same way. Water or 
soft food of any kind should then be swallowed and vomit- 
ing continued, so as to remove all traces of the poison. 

The second thing is to give castor oil or salts, so as to 
remove any poison which may have entered the intestine. 

The third thing is to give something, called an antidote, 
which will destroy the poison in the body. 

The fourth thing is to give a stimulant, for the person 
will be very weak. Strong coffee should be given by the 
cupful, without sugar or milk. 

256. Poisoning by acids or alkalies. — If the lips and 
mouth are covered with a white film or are raw, some 



I50 APPLIED PHYSIOLOGY 

acid or alkali has probably been swallowed. If it is an 
alkali, a drink of weak vinegar should be given at once as 
an antidote. If it is an acid, soda, soapsuds, or limewater 
should be given as an antidote. 

Also give water, or flour and water, or the white of an 
^gg, or milk, so as to dilute the substance as soon as 
possible. 

257. Carbolic acid. — When swallowed, pure carbolic 
acid produces great weakness and rapid death. In small 
doses, or even applied to the skin in surgical dressings, it 
may produce headache and weakness, which may result in 
death. 

In treating its poisonous effects, a stomach pump will 
generally have to be used to remove the poison, because 
the stomach will be paralyzed by the burning to which it 
is subjected. The antidote is Epsom salts. 

258. Narcotic poisoning. — If the person poisoned is 
sleepy, it shows that a narcotic like opium or chloral has 
been taken. Care should be taken not to mistake a faint- 
ing spell for the drowsiness of poisoning. In faintness, 
the face is of a deathly pale color, and no pulse can be 
felt, and breathing ceases, while in drowsiness the face is 
of a natural or even deeper red color, the pulse can be 
felt, and breathing will continue. 

259. Strychnine poisoning. — Strychnine produces vio- 
lent convulsions, like lockjaw, within half an hour after it 
has been taken. Vomiting should be induced at once. 
Chloral and bromide of potash are its antidotes, and 
should be given as soon as possible, to quiet the convul- 
sions. In an emergency tobacco may be used. 

260. Arsenic and other metals. — Rat poison and Paris 
green contain arsenic. Arsenic is a metal, and its poison- 
ing is much like poisoning by merciiry^ lead^ coppeVy silver^ 



DRUGS AND POISONS 151 

or antimony. Sugar of lead and zvhitc lead paint are the 
common forms of lead which poison the body. Copper 
is seldom dangerous. Some forms of silver are very 
poisonous. 

Antimony is poisonous in the form of tartar emetic and 
wine of antimony, both of which are used in treating colds. 

All forms of metallic poisoning are much alike. Vomit- 
ing usually comes on within half an hour, followed by 
great weakness, cramps in the abdomen, and burning thirst. 
If vomiting has not freely occurred, it should be induced 
by tickling the throat or by giving mustard in water. 

Aftenvards the white of eggs, flour paste, or milk should be given as 
an antidote. The albumin of these substances forms a chemical union 
with the metal, producing a harmless compound which should be 
vomited and more of the antidote given. 

The special antidote for arsenic is oxide of iron. The settlings which 
form in a mixture of tincture of iron and baking soda may be used in an 
emergency. The special antidote for tead is Epsom salts; for silver, 
conn/ion salt ; and for antimony, tannin, which is found in a strong tea 
made of almost any bark. 

261. Phosphorus. — Phosphorus poisoning may occur 
from sucking the ends of matches. It produces vomiting 
and violent cramps in the abdomen for two or three days, 
and then jaundice appears, with delirium and death. It 
resembles a slow poisoning by a metal. 

Phosphorus poisoning is treated by giving something to cause vomit- 
ing and to expel the poison from the intestine. Always avoid castor 
oil or other fat, for phosphorus is dissolved by fat. A small pinch of 
sulphate of copper (blue vitriol) given every few minutes will destroy 
the poison and also cause vomiting. 

262. Aconite. — Aconite produces extreme weakness of 
the whole body. A tingling in the throat is the only dis- 
tinguishing sign of the poison. 



152 APPLIED PHYSIOLOGY 

A poisoned person should be kept absolutely quiet, and 
strong coffee should be given as a stimulant. 

263. Belladonna. — Belladonna, or its active principle, 
atropi?te, is used to enlarge the pupil in examinations of 
the eye. In overdoses it produces redness of the face, 
dryness of the throat, enlargement of the pupil of the eye, 
delirium, and great weakness. The enlarged pupil is its 
distinguishing sign. Its treatment consists in giving an 
emetic, stimulating by coffee, and giving tannin or strong 
bark tea. 

264. Mushroom poisoning. — Poisonous mushrooms pro- 
duce violent cramps in the abdomen, with vomiting and 
great weakness. One form produces symptoms within an 
hour or two, and is seldom fatal, for the poison is thrown 
off. The other, and by far the more dangerous, form of 
poisoning does not come on for ten or twelve hours, or 
until the poison has entered the intestine. In poisoning 
by mushrooms, vomiting should be induced, and castor oil 
given to remove the poison from the intestine. Strong 
coffee should be given as a stimulant. 

265. Decayed food. ^ — All forms of decayed food, espe- 
cially fish, eels, and crabs, may produce vomiting, cramps, 
and weakness, like mushroom poisoning. The symptoms 
usually come on within six hours after eating, and are seldom 
fatal. The treatment is to empty the stomach and intestine. 

266. Alkaloids. — • The active principles of many vege- 
table drugs can be separated from the crude drugs. They 
are called alkaloids. Nicotine, morphine, strychnine, atro- 
pine, and quinine are alkaloids. Over one hundred in all 
are known. A single grain of almost any alkaloid except 
quinine can produce violent poisoning. 

267. Leucomaines. — As a result of the imperfect oxida- 
tion of albumin within the body, compounds resembling 



DRUGS AND POISONS 1 53 

alkaloids are formed. They are called Icucomaincs. They 
circulate in the blood and produce headaches, drowsiness, 
and other mild forms of poisoning which may become 
severe and produce death when, as in Bright's disease, 
the kidneys and skin do not remove the poisons. At least 
sixteen leucomaines are known. 

268. Ptomaines. — As a result of decay and other changes 
after death, another set of poisons like alkaloids and leuco- 
maines are produced. They are called ptomaines. They 
cause most of the symptoms produced by eating decayed 
meat. A special kind of the poison, called tyrotoxicon, 
sometimes forms in milk and ice cream which has been 
kept for some time. Ptomaines and leucomaines can 
always be found in the bodies of dead persons. 

269. Hypodermic injections. — When injected beneath the 
skin by means of a hypodermic needle, drugs and poisons reach the 
blood at once and produce much more powerful and rapid results than 
when absorbed from the stomach. Alkaloids are well fitted for this use. 

270. Snake bites. -—In the upper jaw of a poisonous 
snake is a sharp, hollow tooth, which is the outlet for 
a bag of poison. When the snake bites, the pressure of 
the flesh against the bag forces some poison through 
the tooth, which thus acts as a hypodermic needle. The 
poison is a kind of leucomaine. It produces pain and 
swelling at the point of injection, great weakness of the 
whole body, and sometimes death. 

The treatment of snake bites must be prompt. A 
handkerchief should be tied very tightly round the limb, 
above the wound, so as to prevent the poison from reach- 
ing the whole body. Then the wound should be sucked 
for some time, so as to remove as much as possible of the 
poison. No harm can come to the person who sucks the 
wound if the blood is spit out at once. If bleeding does 



154 APPLIED PHYSIOLOGY 

not take place freely, the wound should be cut open. 
Active stimulation with such substances as strong coffee 
or ammonia is also necessary. 

271. Insect stings and bites. — Bees, wasps, and hornets pos- 
sess a hollow sting through which the insect injects poison into the flesh. 
This poison produces swelling and pain, and if there are a great num- 
ber of stings, there will also be a considerable weakness of the whole 
body. Usually the swelling begins to decrease within an hour. To 
allay the smarting, a lump of cold mud is an effective remedy. Carbolic 
acid in water sopped on with a cloth is also good. If the insect has 
left its sting in the flesh, it should be removed by pressing over the 
sting with the open end of a watch key, or by picking it out with the 
point of a sharp knife. 

The bites of mosquitoes and of flies produce swelling and pain or 
itching in some people. Ammonia water or carbolic acid in water 
usually gives relief. 

SUMMARY 

1. Disease is a derangement in the action of some of the 

cells of the body. Drugs either stimulate or retard 
the action of the cells. 

2. All narcotics and drugs are poisons. 

3. In every case of poisoning the stomach and intestine 

should be emptied at once, and a stimulant with 
an antidote to destroy the poison should be given. 

4. Spoiled or poisonous food produces stomach and intes- 

tinal disturbance. It should be expelled from the 
body as soon as possible. 

5. The active principles of many vegetable drugs are 

called alkaloids. 

6. Leucomaines and ptomaines are substances resembling 

alkaloids, but are produced in the bodies of animals. 

7. The poisons of snakes and insects are substances 

like leucomaines, and are injected into the flesh by 
means of a hollow tooth or sting. 



DRUGS AND POISONS 1 55 



REVIEW TOPICS 

1. Describe the nature of disease and how drugs tend to 

restore health. 

2. Describe the general signs and treatment oi poisoning. 

3. Describe the treatment of poisoning by acids, and by 

alkalies. 

4. Describe carbolic acid poisoning and its treatment. 

5. Distinguish between the drowsiness due to narcotic 

poisoning and a fainting spell. 

6. Describe strycluiinc poisoning and its treatment. 

7. Describe poisoning by arsenic and give its treatment. 

8. Give the signs and treatment of poisoning by metals 

in general. 

9. Describe phosphorus poisoning and give its treat- 

ment. 

10. Describe poisoning by aconite ; by belladojina. 

11. Describe poisoning by mushrooms, and by decayed 

food. 

12. Describe alkaloids, leucomaines, ptomaines, and their 

poisonous effects. 

13. Describe hypodermic injections. 

14. Describe snake and insect bites and give the treatment. 



CHAPTER XVIII 

THE BLOOD 

272. The circulatory system. — Nature has provided an 
intricate arrangement of tubes to conduct food to each cell 
of the body, and to wash away its waste matter. These 
two objects are accomplished by the blood. The conduct- 
ing tubes and the blood which they contain make the 
circulatory system. 

273. The blood. — About one thirteenth of the body is a 
red liquid called blood. It consists of a multitude of cir- 
cular flat red plates, called the red blood corpuscles or cells, 
floating in a colorless liquid, which also contains a few 

round colorless cells, called white blood 



Jt^ T 'T' corpuscles or cells. 
(2) (o) @ ©^ ^ 

* © ®«^® @ 274. Red blood corpuscles. — The red 

c 8 ii @® corpuscles of the blood form about 45 per 

Blood corpuscles cent of its weight. Each one is a circular 

(X 400). ^^^ plate, with rounded edges, and with 

a a pile of red blood i • • ^i i. r i r 

^g]is a depression m the center of each face. 

b red blood cells, Each Cell is about 3-^^00" of an inch in 
c rer^biooT'ceiis, diameter and 12^00 of an inch in thick- 
seen edgewise, ^ess. Each one is of a reddish yellow 

d white blood cells. mi 

color, but when great numbers are piled 
together they appear bright red. Each corpuscle is com- 
posed of a jellylike albuminous substance, four fifths of 
which is a reddish substance called hemoglobin. Hemo- 

156 



THE BLOOD • 1 57 

globin is the essential part of the red corpuscle. It con- 
tains a small amount of iron, which gives to it the prop- 
erty of carrying oxygen without itself being oxidized. By 
means of the hemoglobin the red corpuscles are able to 
carry oxygen from the lungs to all parts of the body. 
When the hemoglobin contains a large amount of oxy- 
gen the blood is of a bright red color, but as the oxygen 
is used up it becomes darker, or almost purple. Bright 
red blood, called arterial blood, is continually flowing 
toward the cells of the body ; while that returning from 
the cells, called venous blood, is purple in color, from the 
lack of oxygen. 

275. White corpuscles. — White corpuscles are each 
about g^oVo ^^ ^^"^ ixioh in diameter, and are about -^\-^ as 
numerous as the red corpuscles. 
They are round and colorless, and 
each contains a nucleus. They 
have the power of changing their 
shape, and of adhering to the 
sides of a blood tube, and of 
passing through its wall, and of 
moving about between the cells 

^ , , - , . , 1 A white blood cell of a frog, 

of the body as though endowed sketched at intervals of two 

with a will of their own. They or three minutes, showing its 

. changes in form (x 300). 

have important duties to pertorm 

in preventing foreign substances from entering the circula- 
tion and in the healing of wounds. (See p. 393.) 

276. Plasma. — The Hquid part of the blood is called 
the plasma. It is composed of ninety parts of water, 
holding in solution about eight parts of albumin and two 
parts of mineral matter. The mineral matter is mostly soda 
and potash. This alkaline property of the blood plasma 
aids it in dissolving carbonic acid gas, and in carrying it to 




158 



APPLIED PHYSIOLOGY 



the lungs, where it is breathed out from the body. 
Some of the mineral matter of the blood enters into the 
composition of the cell^ of the body, especially of bone 
cells. 

The albumin is the substance out of which all of the 
cells of the body are mainly built. It is formed by 
the liver out of the peptone which was absorbed from the 
intestine. A little pressure causes the solution of albumin 
and minerals to flow through the sides of the capillaries ; 
and thus it reaches the separate cells of the body. Waste 
matters are continually being poured into the plasma, but 
they are removed as fast as they enter, so that carbonic 
acid is the only one to be found except by the most deli- 
cate tests. 

277. Clotting. — When blood is drawn from the body it 
soon becomes a jelly like mass, called a clot. After a longer 
time the clot becomes firmer and smaller, squeezing out a 
clear, straw-colored liquid, called sentm. The process of 
changing blood from a liquid to a jellylike form is coagu- 
lation, or clotting. In the process a part of the albumin 
becomes solidified in small interlacing strings, called 
fibrin, which entangles the rest of the blood into its 
meshes. The network soon contracts, squeezing out the 
serum, and retaining the corpuscles. The serum is com- 
posed of all the materials of the plasma, excepting the 
fibrin. The process may be represented thus : 



albumin 
+ 

Plasma or \ mineral matter 
+ 
. water 



Serum, or 



Corpuscles 



Clot, or 



albumin 

+ 
mineral matter 

+ 
water 
fibrin 



[ corpuscles 



THE BLOOD I 59 

While the blood is in motion within a healthy blooci 
tube, no clotting occurs, but as soon as blood is drawn, 
it clots, or if a blood vessel is wounded, a clot forms at 
the wounded spot. The use of clotting is to stop bleeding. 
Sometimes no clot will form, but a wound will keep on 
bleeding until it is healed. This is a disease called Jienio- 
pJiiIia, and may cause death. 

278. Anemia. — Sometimes there are too few red cor- 
puscles in the blood. Then the skin appears pale and 
there is shortness of breath, because too little oxygen is 
carried by the diminished number of red blood cells. The 
disease is called anemia, meaning lack of blood. It is 
mainly a lack "of red corpuscles. 

279. Good and bad blood. — The terms good and bad blood 
are remnants of the old idea that disease was caused by watery sub- 
stances, called humors^ in the blood. From their supposed influence 
on the mind the terms good and bad humored are derived. 

For many years attempts have been made to inject healthy blood 
into the veins of sick persons. Injecting a liquid into the veins of a 
living person is trajisfusion. In bleeding, the loss of water is one of 
the greatest dangers, and to replace it water is sometimes injected into 
the veins. It answers better than blood itself. 

280. The blood in lower animals. — All living beings 
possess some form of fluid circulating in their interior. 
In higher animals, birds, reptiles, and fishes, the fluid is 
red, and contains both red and white corpuscles. In 
insects the blood is usually white or colorless. In worms 
the blood is sometimes colorless and sometimes red or 
green. In shellfish the blood is colorless, and contains no 
corpuscles. In animals which are made up of a single 
microscopic speck of matter, there seems to be a continual 
motion of fluid within their bodies, although they are so 
extremely small that nothing definite can be seen. 



l60 APPLIED PHYSIOLOGY 

281. The spleen. — The spleen or milt is a soft red 
or^-an, shaped like a tongue, lying just to the left of the 
stomach. It is composed of small cells and fibers, among 
which the blood circulates as through a sponge, without 
being held within firm walled tubes. The spleen is sup- 
posed to form the red blood cells, but they are also formed 
in the marrow of bones. The spleen can be removed with 
but little harm to the body. The pain in the side caused 
by running is often due to an excess of blood in the spleen. 

SUMMARY 

1. Blood is composed of a liquid called plasma, in which 

float great numbers of extremely small red cells, and 
fewer white cells. 

2. The red cells carry oxygen from the lungs to the cells 

of the body. 

3. The white cells repair injuries to the body. 

4. The plasma contains albumin and mineral matters, 

both of which are food for the cells of the body. 

5. The soda of the plasma carries carbonic acid gas to the 

lungs. The gas is there given off in the breath. 

6. After standing outside of the body for a few minutes, 

some of the albumin hardens to a stringy mass and 
entangles the cells, forming a clot. 

7. All animals possess a fluid somewhat like man's blood. 

8. The spleen is a soft organ in which red blood cells are 

formed. 

DEMONSTRATIONS 

64. Set aside a spoonful of chicken'' s blood to clot. In a few hours the 
serum will begin to separate. Breathe on a slide and place a tiny drop 
of fresh chicken's blood upon it, cover it with a cover glass and exam- 
ine it with a microscope magnifying at least 200 diameters to see the 
red blood cells. Notice their oblong shape and their nuclei. 



THE BLOOD l6l 

65. Human blood may be obtained without pain by tying a string 
snugly around the linger. After a moment make a quick prick with 
a clean needle upon the back of the finger just behind the nail. Remove 
the string, and a drop of blood will flow which can be examined under 
the microscope. Notice the circular shape of the red cells and the 
absence of nuclei. Notice that they tend to arrange themselves in rows 
like piles of coins. 

66. Place a drop of salt water on the slide by one edge of the cover 
glass, and notice that the cells become shrimken. 

67. Uliite blood cells are too few in number to be readily found 
within a specimen of blood, but they form most of the white matter of 
a pimple or boil. Prepare and examine a specimen, and notice the 
dark specks scattered through the cells, and the nuclei which may be 
three in number in each cell. Add a drop of vinegar and notice that 
each cell becomes transparent, only the nuclei remaining visible. 

68. With a little care the movement of the white cells may be shown 
in frog's blood. Prepare a fresh specimen of frog's blood upo.n a slide 
slightly warmed. After a little search an irregularly shaped white blood 
cell can usually be found. Watch it carefully, and it will be seen slowly 
changing its shape exactly as an ameba changes, only more slow^ly. A 
magnifying power of at least 200 diameters will be necessary. 

69. Prepare a specimen of blood for the microscope. (See demon- 
stration No. 65.) At the edge of the cover glass drop a tiny bit of 
alcohol. Notice how the red blood cells shrivel and become irregular 
in form, because the alcohol takes away their water. 

REVIEW TOPICS 

1. Describe the blood. 

2. Describe the red blood cells. 

3. Describe the white blood cells. 

4. Describe the blood plasma. 

5. Describe the clotting of blood. 

6. Show what was meant in olden times by the terms good 

and bad blood and good and bad humored. 

7. Describe the blood in some of the lower forms of living 

beings. 

8. Describe the spleen and its use. 

OV. PHYSIOL. — 1 1 



CHAPTER XIX 



THE HEART 




282. The heart. — The blood is kept flowing through all 
parts of the body by the Jieart. The heart is essentially a 

hollow shell of muscles, which 
has the power of squeezing its 
sides tightly together, so as to 
force out the blood. It is coni- 
cal in shape. Its side lies upon 
the diaphragm, with its tip 
pointing downward, forward, 
and to the left. Its small end 
touches the chest wall about 
two and a half inches to the 
left of the lower end of the 
sternum or breastbone, and its 
large end extends along the 
right side of the breastbone, 
from its lower end upward as 
high as the third rib. It is 
almost covered by the lung, 
and is inclosed in a bag of 
serous membrane called the 
;;; ascending vena cava. pericardmm. The pericar- 

dium is very smooth, so as to permit free movements of 
(See cut, p. 66.^ 
162 



The heart. 

a right ventricle. 

b left ventricle. 

c artery between the two ventricles, 

nourishing the heart's muscles. 

d pulmonary artery. 

e left auricle. 

f aorta. 

g artery to left side of head. 

/^ artery to left arm. 

i artery to right side of head. 

/ artery to right arm. 

k descending vena" cava. 

/ right auricle. 



the heart within it. 



THE HEART 



163 



designed to 
Its left side 



283. Cavities of the heart — The heart is 
pump two separate streams of blood at once, 
pumps blood through the 
whole body, while its right 
side pumps it only through 
the lungs. The cavity on 
each side is partly divided 
into an upper chamber called 
an auricle, and a lower one 
called a ventricle. Each 
auricle has thin, flabby walls, 
and does little of the work of 
pumping blood. 

The ventricles have thick 
and strong walls, which form 
nearly all the bulk of the 
heart. The left ventricle has 
walls three times as thick as 
the right ventricle, for it must 
pump blood through a much 
greater part of the body. 
From each ventricle a tube, 
called an artery, conducts the 
blood away. 

284. Valves of the heart. 
— Blood enters each auricle 
through tubes called veins, 
and streams through the 
opening into the ventricle, 
but is prevented from flow- 
ing back by thin, strong cur- 
tains which are attached to the edge of the opening and 
hang suspended in the ventricle. From the edges of each 




Valves of the heart. 

a artery with its lower ehd split open. 

b vein leading into the heart. 

c auricle with the front cut away. 

d cut edge of the auricle, showing its 

thinness. 
e semilunar valves; their upper edges 

are free and movable. 
/ mitral valve spread open. 
g strings from the edge of the curtain 

of the valve to steady it. 
h muscular projection upon the inside 

of the ventricle to which the strings 

are attached. 
i indentations upon the inner surface of 

the ventricle. 
j wall of the ventricle, showing its thick- 
ness as compared with that of the 

auricle, d. 



164 



APPLIED PHYSIOLOGY 



curtain fine threads extend to projections upon the muscu- 
lar walls of the ventricle, to keep the curtains smooth and 
straight. Blood flowing from the auricle into the ventricle 
readily separates the curtains, but blood pressing upon 
them from the ventricle forces them tightly together, so 

that not a drop can pass 
through. Thus they form 
a valve in each opening. 
The valve upon the left 
side is composed of two 
curtains, and is called the 
mitral valve. The one 
on the right side is com- 
posed of three curtains 
and is called the tricuspid 
valve. From their situa- 
tion, these valves are 
often called the aiiriculo- 
ventricidar valves. 

285. Semilunar valve. 




Systole of the heart. 

a vein entering the auricle, 

b auricle. 

c closed valve to keep blood from flowing — At the beginning of 



back into the auricle. 
d ventricle. 
e artery. 
/ valve to keep blood from returning to the 

ventricle. 



each artery leading from 
the ventricles are three 
thin, silklike flaps, shaped 
. like half-moons. They 
are arranged so that blood flowing from the ventricle pushes 
each flap against the side of the artery ; but between the 
beats of the heart, the blood in the artery presses backward, 
forcing the flaps away from the side of the artery, so that 
they all meet tightly in the middle. They form a valve 
called the semilunar valve, from the shape of each flap. 

286. Action of the heart. — The heart is a pump with 
valves permitting blood to flow through an auricle into a 



THE HEART 



[65 



ventricle and out into an artery, while preventing any flow 
in the opposite direction. 

As blood enters the heart it passes through the auricles 
into the ventricles. Just before the ventricles are full the 
auricles suddenly contract and drive the blood into the 
ventricles, which are 
thus filled full and im- 
mediately begin to con- 
tract, while the auricles 
relax. The pressure 
closes the mitral and 
tricuspid valves and 
opens the semilunar 
valves. The blood is 
thus prevented from 
flowing back to the auri- 
cles, but flows through 
the open entrance to the 
arteries. During the 
contraction of the ven- 
tricles, the auricles re- 
main relaxed and receive 
the blood returning to 
the heart. 

When all the blood is 
expelled from the ventricle it relaxes, and the blood falls 
back upon the semilunar valves, closing them so that none 
returns. At the same time the blood in the aurxles presses 
open the mitral and tricuspid valves, and again fills the 
ventricles. 

287. Rate and time of the heart's action. — The contrac- 
tion of the heart is called its systole, and its relaxation its 
diastole. At each systole from two to four ounces of 




Diastole of the heart. 

a blood entering auricle. 

b auricle. 

c open valve to permit blood to flow into the 

ventricle. 

d ventricle. 

e artery. 

/ closed semilunar valve. 



1 66 APPLIED PHYSIOLOGY 

blood are expelled. It occurs about seventy-two times 
each minute. While the heart beats occur regularly 
without apparent pause, yet it rests in diastole about 
one half the time. 

288. Sounds of the heart. — Two sounds are produced by each 
beat, which may be heard by listening with the ear close to the heart. 
The first sound is the longer and softer, and is caused by the vibration 
of the contracting muscles. The second sound is shorter and sharper, 
and is caused by the sudden closing of the semilunar valves. At each 
systole the portion of the heart touching the wall of the chest may be 
felt to become suddenly harder, as though it beat against the chest 
wall. Its movements are transmitted through the chest walls so that 
they may be plainly seen and felt. Ordinarily a person is not aware of 
his own heart beats, but when they are very forcible they are plainly 
felt, and are called palpitation. 

289. Nerves of the heart. — A nervous mechanism within 
the heart itself causes it to contract even after it is sepa- 
rated from the body. A fish's or turtle's heart will con- 
tract regularly for hours after being removed from the 
body. Man's heart is easily affected by outside influ- 
ences, but, because of its own nervous mechanism, it is 
not so sensitive as has been supposed. Wounds com- 
pletely penetrating the ventricle have been sewed up, and 
recovery has taken place. The action of the heart is regu- 
lated and adapted to the varying needs of the body through 
two sets of nerves, one set from the brain and the other 
set from the spinal cord. In physical exertion the spinal 
nerves cause it to beat faster and more forcibly. This 
adaptation is so delicate that rising from a sitting to a stand- 
ing position perceptibly increases the number of heart beats. 
Joy, or anger, or excitement of any kind hastens its action, 
while grief usually retards and weakens it. 

290. Effect of violent exercise. — In prolonged and vio- 
lent physical exercise the heart performs more work than 



THE HEART 167 

is natural, and grows larger to accommodate itself to the 
strain. Repeated calls to extra exertion may cause it to 
respond more quickly and with more vigor than occasion 
demands, so that a slight excitement or exertion causes 
palpitation. Those who engage in races are especially 
liable to overwork their hearts. 

291. Palpitation of the heart. — The response of the heart 
to influences from the outside may be excessive, so that it beats too 
quickly and more forcibly than occasion demands. Sudden noises, 
and excitement of any kind, cause the heart to beat violently or palpi- 
tate in some persons. But palpitation of the heart is an annoyance 
rather than a disease. While the will has no control over the heart, 
yet it can control the emotions which cause the palpitations. Persons 
of calm temperament, who exercise self-control over their emotions, are 
rarely troubled with palpitation. Our words ending in "hearted,''' as 
" warm-hearted," are records of the old belief that the heart governed 
the feelings instead of the feelings affecting the heart. 

292. Fatty heart — The heart may become diseased, 
but heart disease is by no means so dangerous as is com- 
monly supposed. In fact, those having diseased hearts 
are usually unaware of it for years, while, on the other 
hand, those who think their hearts are diseased are almost 
always mistaken. 

There is a common change of the heart's muscle, in which little 
particles of the muscle cells are changed to fat. The cells are thus weak- 
ened, and made unable to respond to a sudden extra demand. A per- 
son with excessive development of fat elsewhere, is liable to have a 
fatty heart. Avoidance of things which tend to cause excitement and 
overwork will enable such a heart to work on without noticeable change 
in its actions. 

293. Disease of the valves of the heart. — The other 
common form of heart trouble is a thickening and puck- 
ering of the valves, causing a leakage so that some blood 
flows backward. But the heart grows larger and stronger, 



1 68 APPLIED PHYSIOLOGY 

SO that it can pump enough blood to supply the body in 
spite of the constant leakage backward. The heart may 
thus become twice its natural size, but there is a limit to 
its enlargement, and finally it grows weak. If exertion 
is avoided, such a heart may work perfectly for years. 

The nervous system contained in the heart's muscle makes it the 
most resistant of all the organs of the body, and the one whose disease 
is least to be feared. It is the first organ formed in the child, and is 
the last to die. When it begins to fail, the blood accumulates in the 
lowest parts of the body, and produces swelling of the feet, which is 
one of the first signs of heart disease. 

294. Fainting. — When the heart is suddenly checked 
and made weak in its action to such an extent that little 
blood is driven to the brain, unconsciousness and complete 
loss of muscular power result, so that the person falls to 
the ground. The face appears pale, because there is but 
little blood in it. This paleness and loss of consciousness 
is called /^7/;^//;/^. When a person faints he should be laid 
upon his back with his head as low as his body, so that the 
blood may flow to the brain more easily. Cold water should 
be thrown upon the face so that the sudden shock may 
stimi 'ate the spinal nerves which hasten the heart's action. 
In a .. iw seconds the heart beats become stronger, and con- 
sciousness is regained. Remember not to raise the head 
of a fainting person. 

295. Effects of alcohol upon the heart. — The first effect 
of alcohol is to increase the force and frequency of the 
heart beats. This sends more blood through all the body, 
and there is a feeling of greater strength, which is called 
stimtilation. Men take strong drink for this effect. This 
feeling comes on within a few minutes after drinking 
and passes off in the course of an hour. Then the 



THE HEART 169 

drinker feels a desire for more alcohol and so forms a 
habit of its use. While a little alcohol may make a man 
feel better, yet the strength and endurance of his heart 
is really diminished. Alcohol is like a whip which makes 
the heart beat harder for a time but leaves it less able 
to do its work in the future. Its blow is pleasant at the 
time it is given, but it is all the more harmful because 
it is enjoyed. 

296. Effects of continuous .drinking. — The derangement 
of digestion and assimilation resulting from long-continued 
drinking impairs the nutrition of the whole body, includ- 
ing the heart. Drinkers confound the absence of fatigue 
with strength itself. 

297. Effects of tobacco upon the heart. — Tobacco used 
in any form is a direct poison to the heart's muscle and 
causes it to beat with less strength. When a large amount 
is used, it poisons the nerves of the heart and hinders their 
harmonious action. Then the heart will beat irregularly, 
and there wdll be palpitation on slight exertion, so that 
hard physical exercise becomes an impossibility. The 
trouble may be only an inconvenience, so that the person 
cannot engage in violent exercise ; but in its severe forms 
it may be the cause of death. 

SUMMARY 

1. The blood is kept in constant motion by a double 

muscular pump, called the Jieart. 

2. The heart contains two pairs of cavities, each con- 

sisting of an njiricle and voiti'icle. 

3. Between each auricle and ventricle there is a valve 

which permits blood to flow into the ventricle, but 
keeps it from flowing back. 



170 APPLIED PHYSIOLOGY 

4. Each ventricle contracts upon the blood about seventy- 

two times a minute, forcing it out through a tube 
called an artery. 

5. Blood is kept from running back into the heart by a 

valve at the beginning of the artery. 

6. The heart contains a nervous mechanism which 

makes it partially independent of the rest of the 
body. 

7. The heart has great power of resistance against 

disease, and of accommodating itself to increased 
work, so that heart disease is less to be feared 
than disease of almost any other part of the 
body. 

8. AlcohoF at first causes the heart to beat faster and 

more strongly than the body needs, thus causing 
it to tire itself out. 

9. Alcohol soon weakens the heart by impairing its nutri- 

tion. 
10. Tobacco makes the heart beat irregularly and with 
less power. 

DEMONSTRATIONS 

70. The left side of a chicken's heart closely resembles a man's 
left auricle and ventricle, and can be used to show the cavities and 
valves. In removing it, be careful to preserve its covering of peri- 
cardium. A pig's, or sheep's, or bullock's heart is more like a human 
heart. The butcher should be instructed not to cut off the auricles. 
(See demonstration 35.) 

71. Tlie heart of a frog or fish which has just been killed should be 
removed to show its persistence in beating. (See demonstration 35.) 

72. Have the students listen to each other's hearts so as to get 
a clear idea of the two sounds. Feel the heart beats upon the chest, 
and notice how they increase in force and frequency when a person 
rises after lying down, and more yet when he walks and runs. 



THE HEART I /I 

REVIEW TOPICS 

1. Describe the heart: its situation, pericardium, cavi- 

ties, and valves. 

2. Describe the action of the heart and the flow of blood 

through it. 

3. Describe what may be heard, seen, and felt by examin- 

ing the body over the heart. 

4. Describe the nervous mechanism of the heart. 

5. Give the effect of violent exercise upon the heart. 

6. Discuss palpitation of the heart. 

7. Describe a fatty heart. 

8. Describe how the valves of the heart may be diseased, 

9. Describe fainting and its treatment. 

10. Give the effects of alcohol upon the heart. 

11. Give the effects of tobacco upon the heart. 



CHAPTER XX 



THE FLOW OF BLOOD IN THE BODY 

298. Arteries. — The tubes which conduct the blood 
away from the heart are called ai'tciaes. From the left 

ventricle there goes a single 
tube called the aorta. It 
gives off branches, which 
subdivide again and again, 
until they are of micro- 
scopic size and penetrate 
to every part of the body. 
From the right ventricle 
there extends another tube, 
called \}i\Q, piilmonaiy artery^ 
which conducts blood only 
to the lungs, where it is 
purified. 

299. Structure and action 
of arteries. — An artery is a 
muscular tube covered with 
a tough layer of connective tissue and lined with a layer 
of very smooth, platelike cells. Its muscle can diminish 
the size of the tube. The arteries are elastic, and are 
always so full of blood that they are somewhat distended. 
At each systole of the heart, from two to four ounces of 
additional blood are suddenly forced into the already full 
aorta. During the heart's diastole, the elasticity of the 

172 




An artery cut across (x 200). 

a smooth inner coat. 

b middle or muscular coat. 

c outer or connective tissue coat. 

d small artery to nourish the large one. 



THE FLOW OF BLOOD IN THE BODY 



173 



artery causes it to contract, forcing the blood onward in 
a steady stream. But the artery can exert no more power 
in contracting upon its blood than the heart exerted in 
distending the artery, and so it is really the heart's force 
which propels the blood. 

300. The pulse. — The extra distention of the aorta by 
each systole of the heart produces a wave in the blood 
which runs along the arterial tubes. Wherever an artery 
runs near the surface, as in the wrist, the wave may be 
felt, and is called the pulse. The pulse is not a sudden 
current of blood shot through the artery, but is a wave 
in the steady stream. By means of the pulse the fre- 
quency and regularity of the heart beats may 
be determined. When an artery is cut, a 
continuous jet of blood spurts out to a con- 
siderable distance, which momentarily in- 
creases in size with each wave beat. 

301. Capillaries. — The smallest arteries 
suddenly divide into an extremely fine net- 
work of tubes, called capillaries. Each capil- 
lary tube is from 2 oV^ ^*^ 
diameter, and from 

length. It is composed of the same kind of 
smooth and flat cells as those which Hne the 
arteries ; in fact, the capillaries are the pro- Diagram of a 
lons^ation of the linings of the arteries. They capillary, show- 

, 1 1 11 r ing the platelike 

penetrate the spaces between the cells of the cells of which it 

body in such a close network that several ^^ composed (x 

, . . 500)- 

capillaries may be in contact with each cell, 

and the point of a fine needle cannot be thrust into the 

body without wounding some. The blood in the capillaries 

gives the pink tinge to the skin, which disappears when 

the blood is pressed out. The total capacity of the capil- 



00 ^- 3A0 of an inch in 

_JL_ to 
1000 '-" 



gig- of an inch in 




174 



APPLIED PHYSIOLOGY 



laries is about three hundred times that of the arteries, 
and hence the blood pressure is much less than in them ; 

yet the pressure is always 
sufficient to keep the blood 
in steady motion. 



302. Action of the white 
blood cells in the capil- 
laries. — Often a white blood 
cell will adhere to the wall of 
the capillary and partially block 
the blood stream for a moment.' 
It may work its way through 
the wall of a capillary, and yet 
leave no hole behind it. Many 
are thus found in the spaces 
outside the capillaries, and are 
finally returned to the heart by 
means of another set of tubes 
called lymphatics. When a capillary is injured, many of the white 
cells adhere to the injured spot and furnish food for its repair. They 
may even grow and change 




Arrangement of capillaries. 

a smallest artery. 

b smallest vein. 

c network of capillaries. 



to connective 
further repair. 



tissue for its 




303. Diffusion of blood 
plasma in the capillaries. 

— The slight pressure to 
which the plasma is sub- 
jected is just sufficient to 
cause it with its albumin 
to diffuse through the ex- 
ceedingly thin wall of the 
capillary. It fills the 

spaces between the capillary network and bathes each cell 
of the body with an abundant supply of nourishment. 



Diagram showing how food reaches the 
cells from the capillaries. 



THE FLOW OF BLOOD IN THE BODY 1 75 

304. Exchange of oxygen and carbonic acid in the capil- 
laries. — The blood in a capillary is separated from a living 
cell of the body by a wall so thin that it is no hindrance 
to the passage of oxygen from the red blood cells. In 
return for the oxygen received from the blood, the body 
cells give out carbonic acid gas, which passes through the 
capillary walls into the blood as readily as the oxygen 
passes in the opposite direction. A given particle of 
blood remains in a capillary only a second at most, and 
in that time there occurs an exchange of oxygen and 
nutritive matter between the blood and the body cells. 
Arteries are simply tubes which conduct blood to the 
capillaries, where all the actual work of nourishing the 
cells is performed. 

305. Veins. — The network of capillaries at the end of 
each artery unites to form a single tube, called a vein. 
Each vein unites with others again and again, to form 
larger tubes which run alongside of each artery, and finally 
all unite to form two main veins. One vein, called the 
descending vena cava, returns blood from the head and 
arms ; the other, called the ascending vena cava, returns 
blood from the lower extremities and trunk. Each opens 
into the riofht auricle. The veins have about three times 
the capacity of the arteries. Their walls are composed of 
the same material, but are very much thinner, for they do 
not have to stand much pressure of blood. The blood 
current is correspondingly slow. The veins have valves 
at intervals which permit of a free flow toward the heart, 
but oppose its passage backward, so that when a vein is 
pressed the blood is forced only towards the heart. The 
contraction of the muscles pressing upon the veins is 
thus a great aid to the flow of blood, f he flow of blood 
is also aided by the movements of the chest in breathing, 



176 



APPLIED PHYSIOLOGY 



.?^^^^^r^, 



which suck venous blood toward the heart just as it sucks 
air into the lungs. 

306. Pulmonary circulation. — As the . blood enters the 
veins from the capillaries, it has lost some oxygen and 

gained carbonic 
acid gas and other 
waste matter. This 
makes it much 
darker in color. 
Before it is used 
again it is purified 
and given a new 
supply of oxygen. 
For this purpose 
it is sent to the 
lungs as soon as it 
reaches the heart. 
From the veins 
the blood flows in- 
to the right side 
of the heart, and 
then to the lungs 
through the pul- 
monary artery. 
The pulmonary 
artery divides 
again and again 
into small twigs, 
and these divide 
into a close net- 
Diagram of the course of the blood in the circulation, ^^qj.]^ Qf capillaries 

within the lungs, where the blood is separated from the air 
by only the thin walls of the capillaries. Through these 




THE FLOW OF BLOOD IN THE BODY l^y 

thin walls the oxygen of the air readily penetrates to the 
red blood cells; and the carbonic acid gas just as readily 
passes from the blood to the air. As a result of this 
change, the blood becomes of a bright red color, and is 
called arterial blood. From the capillaries of the lung the 
arterial blood is collected into the pulmonary veins and 
carried to the left auricle, and then to the left ventricle, 
where it is ready to make another circuit of the body. 

307. Summary of the circulation of the blood. — In making 

a complete circuit of the body the blood passes through the left auricle, 
and through the ffiiiral valve to the left ventricle ; then past the left 
semilunar valve to the aorta, and then through the arteries to all parts 
of the body ; then through the capillaries into the veins ^ and back to 
the heart ; next through the right auricle, then the right ventricle, 
then through the pulmonary artery to the capillaries of the lu?ig; then 
through the pulmona?y vei7is to the left auricle once more. Thus in 
making the complete circuit of the body, a drop of blood passes through 
the heart twice, and through two different sets of capillaries. The 
circuit of the body in general is called the systemic circulation, and that 
through the lungs is \\\^ puhnonary circulatio7i. 

308. The portal system of circulation. — The blood from 
the capillaries of the stomach and intestine is collected 
into a single vein, called the portal vein, which goes to the 
liver and there divides into capillaries. The liver capil- 
laries can be considered as millions of small tubes which 
are substituted for a few inches of the portal vein. Just 
outside of the liver they empty into three veins which 
open into the ascending vena cava. The circulation 
through the liver is sometimes called the portal circuiatioti. 

309. Time required in the complete circulation. — It re- 
quires about twenty seconds for a drop of blood to go the round of the 
circulation from the left ventricle back to its starting point. All the 
blood passes through the heart about once every two or three minutes. 
All the arteries, except the pulmonary artery, carry bright red arterial 

OV. PHYSIOL. — 12 



178 



APPLIED PHYSIOLOGY 



blood, while all the veins, excepting the pulmonary veins, carry dark 
red or venous blood. 

310. The lymph. — In order to nourish the body, the 
plasma of the blood is continually being diffused through 
the capillaries into the spaces between the living cells. 
Each cell is thus bathed in a plentiful supply of plasma, 
from which it absorbs its nutriment. The spaces also 
contain many white cells, which have left the capillaries. 
The blood plasma and blood cells filling the spaces be- 
tween the cells are called the lymph, and the spaces are 
called lymph spaces. 

The lymph is a thin, colorless fluid. In fact, it is blood 
without the red corpuscles, but with many waste matters 
from the cells of the body added. The lacteals of the 

intestine are also 



lymphatics which 
carry the digested 
fats, and hence 
their lymph is of a 
milky-white color. 
311. Lymphatics. 
— Lymph is con- 
tinually collecting, 
and its removal is 
provided for by 
means of a set of 
tubes, called the 
lymphatics. The 
smallest lymphatic 
tubes are much 




Lymphatics of the head and neck. 
B thoracic duct. 



smaller than a capillary, and their walls are so thin that 
they can scarcely be seen with a microscope. Each begins 
in the open space between a capillary and a cell of the 



THE FLOW OF BLOOD IN THE BODY 1/9 

bod}^ They unite again and again to form about twenty 
main trunks tor each limb. Each trunk extends upward, 
and most of them finally unite to form a tube of the size 
of a goose quill, called the thoj'acic duct. 

The thoracic duct lies upon the spinal column, and 
extends upward into the neck, where it opens into a large 
vein. The lymphatics have numerous valves, all opening 
toward the heart. They prevent the backward flow of lymph. 

312. Lymph nodes. — At irregular intervals the lym- 
phatics open into small, baglike bodies composed of a 
spongy network of fibers filled with 
cells which look like white blood 
cells. Each body is called a lyinpJi 
gland or node. The lymph flows 
through these nodes as water flows 
through a filter. They strain out 
matters which are injurious to the 
system, while their cells envelop 
and destroy poisons. Some of the 
cells also flow on with the lymph 
and become white blood cells. 

The lymph nodes may be felt in 
the neck and groins and armpits, as 
small kernels about the size of a 
grain of wheat or corn. When the 
lymph carries certain kinds of poi- 
sons, they swell up and produce the 
disease called scrofula. In boils, 
erysipelas, and other inflamma- r ^ ^ ^ 

■' ^ Lymph node and vessels 

tions, they swell and become very (xio). 

tender and sometimes break down and form abscesses. 

313. Flow of the lymph. — A little pressure transmitted 
from the blood in the capillaries is exerted upon the lymph, 




I So APPLIED PHYSIOLOGY 

but not enough to force it along the lymphatics. Its flow 
is aided by the pressure of muscles upon the spaces and 
the tubes. Its current is slow and unsteady. It is finally 
poured through the thoracic duct into a vein at the root of 
the neck, where it mingles with the blood. About two 
quarts of lymph pass through the thoracic duct daily. If 
a hollow needle is thrust into the skin, and through it 
water containing medicine is forced, the medicated water 
spreads through the lymph spaces between the living 
cells. Some is taken up by the capillaries, and some passes 
into the circulation by means of the lymph, and produces 
the same effect as though it entered the blood through the 
stomach. 

Sometimes the lymph cannot be removed by the lym- 
phatics so fast as it is poured out by the capillaries. It 
then distends the lymph spaces, producing uniform 
swellings called dropsy. Dropsy can be recognized by a 
small pit remaining when the finger is pressed into the 
skin. 

314. The circulation in lower animals. — Land animals 
and birds possess a heart and blood tubes like man's, and 
their circulation follows the same order. The heart of rep- 
tiles and toads consists of two auricles and one ventricle, 
and the ventricle always contains both arterial and venous 
blood. 

Fishes possess only one auricle and one ventricle. The 
ventricle forces the blood through two sets of capillaries, 
and the circulation is made correspondingly sluggish. 

Insects possess a row of eight or nine sacks connected 
by a tube, with valves opening toward the head. The 
contraction of the sacks forces the blood toward the head, 
where it escapes into the lymph spaces between the cells. 
There are no arteries or veins, and so the blood is slowly 



THE FLOW OF BLOOD IN THE BODY l8l 

forced toward the back part of the body through the 
lymph spaces until it again reaches the tube. Their cir- 
culation is thus like the circulation of lymph in man. 

Shellfish usually possess a heart and arteries and veins. 
In the very lowest animals, like the ameba, there seems to 
be a flow of fluid within the body, but no part of the body 
is set aside for the purpose. 

315. History of the knowledge of the circulation. — The 

ancients thought the heart was the seat of life, because the heart was 
seen to be the first organ formed in an egg which was being hatched. 
The idea was confirmed to them by the heart's constant action, which 
tliey thought was caused by the boiUng of the animal spirits. The 
spirits then flowed away in a sluggish stream through the veins, and 
were not supposed to return to the heart. 

They concluded that the arteries carried only air, because they always 
found them empty after death. They knew nothing whatever of the 
capillaries. They thought that food was carried to the liver and was 
there partly cooked, and was then sent on to the heart where it was 
cooked still further in the heart's vital flame, until it was turned to 
blood. Then it was sent out by way of the veins to irrigate the body. 
The valves of the veins were supposed to oppose its flow and to render 
it sluggish. The boiling in the heart was supposed to heave the chest 
up and down, and cause air to rush in and prevent too great a degree 
of heat. The brain also was supposed to cool the blood. Because of 
its more violent action during physical exertion or emotion, they con- 
cluded that the heart, instead of the brain, was the seat of the mind 
and feelings. We still use the word heart with this meaning in such 
expressions as kind-hearted 2.ndi free-hearted. 

Incredibly few discoveries were made for thousands of years, for 
until within two hundred years the law forbade any one to dissect a 
human body. In 1628 a true explanation of the heart and the course 
of the blood was first published by Harvey, an English physician. 
The only point which he omitted was the explanation of how the blood 
gets from the arteries to the veins. Three years after his death micro- 
scopes were made powerful enough to reveal the capillaries for the 
first time, and thus the truth of our present ideas concerning the cir- 
culation was fully established. 



l82 APPLIED PHYSIOLOGY 



SUMMARY 

1. The tubes carrying blood away from the heart are 

called arteries. They are thick-walled and elastic, 
and in them the blood is under considerable pressure. 
Each heart beat causes a perceptible wave in the 
artery, which is called the pulse. 

2. The arteries divide and finally break up into fine 

tubes called capillaries, which touch each cell of the 
body. 

3. In the capillaries some of the plasma passes outside the 

tubes and bathes the cells in nourishment. Some of 
the oxygen leaves the red blood corpuscles to go to 
the cells of the body. Some carbonic acid gas also 
leaves the cells of the body and combines with the 
plasma within the capillary. 

4. The capillaries join together to form thin-walled vessels 

called veins, which return the blood to the heart. 

5. The plasma which has left the capillaries is called 

lymph. It is returned to the blood by means of a 
set of fine tubes called lymphatics. 

6. The lymphatics unite to form a tube called the thoracic 

duct, which runs up the backbone and opens into a 
vein at the root of the neck. 

7. The right side of the heart sends the venous blood to 

the lungs, where it passes through the capillaries 
and is freed from its impurities, and then returned to 
the left side of the heart as arterial blood ready for 
another circuit of the body. This is called the pul- 
monary circiilatioji. 

8. The venous blood from the stomach and intestine passes 

through a second set of capillaries in the liver. This 
is called the portal circulation. 



THE FLOW OF BLOOD IN THE BODY 183 



DEMONSTRATIONS 

73. The flow of blood in the veins and the action of the valves of 
the vein can be shown by placing a finger upon a vein in the skin upon 
the back of the hand. Then press out the blood by running another 
finger a few inches up the vein. When the second finger is removed, 
notice that the blood does not return in the vein, for the valves stop 
the backward flow ; but if the first finger is removed, the vein at once 
fills up. This is one of the proofs which Harvey used to prove the 
circulation of the blood. 

74. The position of the main arteries upon the limbs should be 
shown upon the body. Remember that they are usually over the middle 
of a joint upon the side toward which it can be bent. Explain that 
wherever a beating can be felt there is a pulse and an artery. 

75. Examine an artery and vein prepared for the microscope. Notice 
its smooth and thin inner layer puckered because of the contraction of 
its outer coats. Next is the muscular layer, each cell wrapped around 
the tube. The next and outermost layer is composed of connective 
tissue. Notice that the main difference between the artery and the 
vein is that the artery is thicker. 

76. Tie a string or a rubber band rather tightly around the finger. 
Notice that in a few minutes the finger becomes purple, cold, swollen, 
and painful. Explain that the string does not exert enough pressure 
to close the thick arteries which are under high pressure, but that it 
readily closes the veins. 

I"] . Show the capillary circulation in a frog's foot. Place the frog 
in a covered glass of water to v.hicli a teaspoonful of ether has been 
added. When it ceases to move, spread its web over a hole cut in card- 
board. A ring of dried mucilage will hold it in place. Examine it 
under a microscope with a magnifying power of about 200 diameters. 
Oval cells will be seen shooting tlirough a network of capillaries. The 
tail of a small fish also will show the circulation. 



REVIEW TOPICS 

Describe the tubes which conduct blood to the cells 
of the body, their structure, situation, arrangement, 
action, and pulse. 



1 84 APPLIED PHYSIOLOGY 

2. Describe the capillaries, their structure, and action in 

regard to nutrition and respiration. 

3. Describe the veins, their structure and action. 

4. Describe the pulmonary circulation and the portal cir- 

culation. 

5. Give the time required for a drop of blood to make the 

complete round of the circulation. 

6. Describe the lymph, the lymphatics, the flow of lymph, 

and the use of lymph. 

7. Describe lymph nodes and give their use. 

8. Describe the circulation in reptiles and toads, in fishes, 

in insects, in shellfish, in the ameba. 

9. Give an outline of ancient ideas concerning the circula- 

tion of the blood, and tell when and by whom the 
true circulation was discovered. 



CHAPTER XXI 
REGULATION OF THE FLOW OF BLOOD 

316. Vaso-motor nerves. — The muscles in the walls of 
the smaller arteries regulate the amount of blood passing 
through them. A special set of nerves, called vaso-motor 
nerves, causes the arteries to contract. When these nerves 
are paralyzed, the muscles relax, and the artery becomes 
fully distended by the pressure of the blood. When any 
part of the body is working, its arteries dilate in order 
to supply a greater amount of blood to the part. 

The vaso-motor nerves are affected by influences from 
the brain. Embarrassment and bashfulness paralyze those 
of the head, so that more blood goes to the face and it 
becomes redder, or blushes. On the other hand, fear and 
grief stimulate the nerves and cause a contraction of the 
arteries, which drives the blood from the face so that pale- 
ness results. Heat applied to the skin causes the arteries 
to dilate, and thus to contain more blood. 

317. Congestion. — More than the natural quantity of blood re- 
maining in a part for some time is called congestion. It is liable to 
injure the cells. Cold causes the arteries of the skin to contract so 
that less blood can pass through them. The blood intended for the 
skin is thus directed through the deeper arteries which already contain 
their full amount of blood. So congestion of the deeper parts often 
results. In this way we get cold in our throats. 

318. Secondary effects of heat and cold. — When heat has 

acted upon the skin for some time it causes a contraction of the blood 
tubes. When first put into a tub a washerwoman's hands become 

185 



1 86 



APPLIED PHYSIOLOGY 



red, but in a few moments they become white and shriveled from the 
contraction of the arteries. 

When cold has acted upon the arteries for some time it paralyzes 
them so that they dilate. When a boy begins to snowball, his hands 
are cold, but after a while his hands glow with redness and warmth 
because the paralyzed tubes admit more warm blood. 



319. Effects of injury upon the arteries. — When injured 
in any way, the injured part becomes red and warmer. 
This is because the same cause which produces the injuries 
also partly paralyzes the smaller arteries, so that they dilate 
and bring an extra quantity of blood for the repair of the 
wounded part. Here, as elsewhere, nature wonderfully 
adapts the body to its surroundings. 

320. Nature's arrest of hemorrhage. — Cut capillaries 
cause only an oozing of blood which collects like drops of 

dew over the whole cut 
surface. Blood does not 
spurt from a cut vein, but 
wells out in a slow stream. 
When an artery is cut, the 
blood flows in a strong jet. 
Bleeding from either of the 
vessels usually stops in a 
few moments. The mus- 
cles of the blood tube 
contract and lessen the 
size of the tube, or even 
entirely shut it up ; the blood also clots in the cut, and a 
small plug of clot extends into the end of the blood tube. 
In these two ways bleeding from small cuts is soon stopped 
naturally. But in a large artery the blood pressure is so 
great that it forces away the clot as fast as it is formed, 
so that bleeding may continue until death occurs. 




Diagram of a bleeding cut. 

a upper edge of a cut. 
b a cut blood tube. 



REGULATION OF THE FLOW OF BLOOD 



1 87 




Natural stoppage of bleeding. 

a upper edge of a cut. 

b blood tube, showing its contracted cut 

end filled with a clot. 
c blood clot. 



321. How to stop a bleeding. — It should be remembered 
that sufficient pressure will instantly stop any bleeding. 
If a hand is placed on each 

side of the cut, so as to — _:z"- ^1?^^^= — — — €f 

hold its edges firmly to- 
gether, no bleeding can 
occur. A second way of 
stopping bleeding is by 
pressing a handkerchief, 
or a finger, or even the 
whole hand, into the 
wound. A third way in 
which bleeding may be 
stopped is by cutting off 
the supply of blood to the part. This may be done by 
tying a handkerchief very tightly around the limb be- 
tween the wound and the heart. The knot in the hand- 
kerchief should lie over the artery, and, if necessary, a 
stick may be inserted under the band and twisted tightly. 
Of these three ways of stopping bleeding, that of compres- 
sion by the hands is the best to use at first. 

322. Position of arteries. — Main arteries run in a general 
direction down the middle of each limb, upon the side on which the 
limb can be bent. Thus in the upper part of the arm, the artery runs 
across the center of the armpit, and then down the inner side of the 
upper arm. At the elbow it lies in the center of the front side of the 
arm. An artery lies upon the thumb side, and another upon the little 
finger side of the front of the wrist. 

In the leg the main artery lies in the middle of its upper part, and 
reappears at the surface in the middle of the bend of the knee. At the 
ankle it is divided into two, one of which is just behind the inner ankle 
bone, and the other runs down the middle of the front of the foot. 

There is a large artery and a large vein in the middle of each side 
of the neck. These positions should be remembered, for they are the 
principal places in which a large blood tube is likely to be wounded, 



i88 



APPLIED PHYSIOLOGY 



and they mark the course of the tubes in case they should need to be 
compressed to stop bleeding. 

323. Repair of wounded tubes. — When a vein is cut 
in two, its ends may grow together again, but when an 
artery is cut, each end of the tube remains permanently 





The left upper arm. 

The dotted line indicates the 
course of the main artery (the 
brachial) . 



The right thigh. 

The dotted line indicates the 
course of the main artery (the 
femoral) . 



closed, and thus the supply of blood to the part is at least 
partly cut off. Branches from an artery communicate 
with other branches which begin a few inches further 
down the same artery. When the artery is cut, these 
communicating branches enlarge, and thus permit the 
natural amount of blood to flow around the wound and 



REGULATION OF THE FLOW OF BLOOD 189 

SO reach the artery below the cut. When capillaries are 
cut, a new set is produced to take their place. 

324. Effect of tight bands. — A tight band will obstruct the 
.flow of blood in the veins, while, unless it is very tight, it scarcely 
affects the arteries. So the blood freely enters a pnrt through the 
arteries, but is held back in the veins below the band, until the part is 
distended with blood, and the proper amount of new arterial blood is 
prevented from entering. As a result the nutrition of the part suffers 
and slight injuries do not heal readily. The veins swell from the extra 
amount of blood they contain, and finally enlarge in places, forming 
what are called varicose veins. Tight garters are common offenders in 
this respect. 

325. Alcohol and arteries. — When a cup of hot coffee 
is swallowed, the temperature of the stomach and of the 
blood in its walls is raised. Then nature at once causes 
the arteries of the skin to become enlarged so that more 
blood may come in contact with the cool air, and thus give 
off the surplus heat. Probably in the same manner the heat 
produced by the destruction of alcohol causes the arteries of 
the skin to dilate so that they contain an excess of blood. 
A red face and nose are well-known signs of drinking. 
This dilation of the arteries is one of the most marked 
and constant effects of drinking. 

326. Alcohol and the nutrition of cells. — Naturally, 
when a part of the body is at work, its blood tubes 
become larger, while those of the resting parts become 
smaller. If the blood tubes of distant parts remain large, 
there will not be sufficient blood to fill those of the work- 
ing part, and thus the part will not be able to put forth its 
full strength. If a part is injured, it cannot get enough 
extra blood to repair itself quickly. Thus wounds will be 
apt to heal slowly, while inflammation will be more likely 
to set in. 



190 APPLIED PHYSIOLOGY 

If a part is continuously supplied with an excess of 
blood by dilated arteries, there is apt to be an overgrowth 
of some of its tissues, especially of connective tissue. An 
excess of this tissue interferes with the action of the work- 
ing cells of the part. This change is apt to occur especially 
in the arteries themselves, making them thick and hard. 
It naturally comes on during old age, but is often hastened 
by the use of strong drink. The affected arteries cannot 
change their size, and so the parts which they supply 
suffer in nutrition. Although an excess of blood may go 
to a part, yet it is not renewed so often as it should be. 

SUMMARY 

1. The muscles in the arteries give them the power of 

becoming smaller or larger in order to regulate the 
amount of blood going to any part of the body. 

2. The contraction and relaxation of the arteries is con- 

trolled by gt set of nerves called vaso-motor nerves. 

3. Heat, cold, work, and mental influences are a few causes 

which excite the action of the arterial muscles. 

4. Contraction of arteries near the surface and dilatation 

of the deeper ones is the common cause of taking 
cold. 

5. Alcohol causes a paralysis of the muscles of the arteries 

so that they may remain permanently enlarged. The 
arteries of the face and stomach are most affected. 

6. Small blood tubes, when cut, bleed for a moment until 

the ends of the tubes contract and a clot plugs them 
up completely. 

7. Large blood tubes may bleed until death occurs. 

Bleeding can always be stopped by grasping the 
part boldly and firmly. 



REGULATION OF THE FLOW OF BLOOD 191 

8. Large blood tubes run down the middle of the limb 

upon the side toward which the limbs are bent. 

9. Tight bands obstruct the flow of blood going from a 

limb, but permit blood to enter. Thus the limb 
swells and the veins enlarge. 

DEMONSTRATIONS 

78. The effect of injuiy upon the arteries can be illustrated b}' scratch- 
ing the arm with the point of a pin. In a few seconds a bright red 
mark appears in its track. 

79. Hold the hand in a basin of hot water. Notice that at first the 
skin is red from the dilatation of the arteries. In course of ten min- 
utes the skin becomes white and puckered, because heat has a second 
effect of contracting arteries. 

80. Show how bleeding can be stopped, by boldly grasping an imag- 
inary cut and holding its edges tightly together. Show how a band 
can be tied loosely around a limb above a cut, and then by means of a 
stick inserted under the band, can be twisted as tightly as one pleases 
so as to control bleeding. 

REVIEW TOPICS 

1. Describe vaso-niotor nerves. 

2. Show how vaso-motor nerves are affected by influences 

from the brain ; by heat and cold ; by injuries. 

3. Describe congestion arid how it is caused by cold. 

4. Give the effects of alcohol upon the contraction and 

dilatation of the arteries. 

5. Give the difference between arterial, capillary, and 

venous bleeding. 

6. Describe how bleeding naturally stops. 

7. Describe three ways of stopping bleeding. 

8. Describe how nature restores the circulation after an 

artery is cut in two ; after a vein is cut ; and after 
capillaries are cut. 

9. Give the effect of tight bands upon the circulation of a 

limb. 



CHAPTER XXII 

THE LUNGS 

327. Oxidation. — Life is a process of oxidation. The 
body is an engine. The living cells are the machinery, 
and both they and the blood are the fuel. The fires are 
lighted at birth, and burn without cessation until death. 

328. Respiration. — In every fire a free draft of air must 
be supplied and the burned products must be carried off. 
So in the body air must enter continually, and the oxidized 
products pass out again. The red blood cells are set apart 
for the special work of carrying oxygen to the rest of the 
cells of the body, v. hile the lungs are arrangements in 
which the red blood cells can obtain oxygen from the air. 
The passage of air into and out of the lungs is breathing. 
Breathing and oxidation together constitute respiration. 

329. Respiratory organs. — An air tube leads from the 
surface of the body to the lungs. The parts of the tube 
from the surface to the lungs are the nose, pharynx, larynx, 
trachea, and bronchi. These parts taken together form the 
respiratory tract. They, together with the lungs and red 
blood cells, form the respiratory system. 

330. The nose. — The nose is a double tube lined with 
mucous membrane. Each tube has a smooth bottom and 
inner wall, but its outer wall is thrown into three curved 
folds extending lengthwise so as almost to form partitions 
across the tubes. The folds warm the air and strain out 
dust as it passes over their surfaces. From each side of 

192 



THE LUNGS 1 93 

the nose a tube extends to the eye to drain away tears, and 
another opening extends into the antrum or cavity in the 
upper jawbone. In the nose there are special nerves of 
the sense of smell. (See p. 324.) 

331. The pharynx. — The pharynx is the muscular bag 
just back of the mouth, through which both food and air 
pass. Air should always enter it from the nose. Just in 
front of the pharynx upon each side is a fleshy body, look- 
ing like an almond, and called the tonsil. Sometimes the 
tonsils become very large in children and close the open- 
ing into the nose, making it necessary to breathe through 
the mouth. 

332. Adenoid vegetations. — In the upper part of the 
pharynx, just behind the opening of the nose, there often 
grows a collection of soft, grapelike bodies, called ade- 
noid vegetations. They close the opening to the nose and 
compel a person to breathe through the mouth. They 
begin to form during early childhood while the bones are 
growing. The unnatural breathing and open mouth de- 
form the upper jaw so that it becomes narrow and poinlM. 
The trouble is a serious one. While it does not cause 
inconvenience in itself, yet it compels mouth breathing ; 
it renders the child very susceptible to taking cold ; and 
is the most common cause of deafness, for it stops the 
Eustachian tube leading to the ear. Often they are asso- 
ciated with large tonsils. 

When a child becomes grown, the adenoid vegetations 
often shrink, and so cure themselves, but the deformed jaw 
lasts through life. They can easily be broken down and 
removed with the finger, as they should be in every case. 

333. Mouth breathing. — The mouth contains no means for 
warming the air, or for screening out dust and disease germs, as the 
nose has. So a mouth breather is very likely to take cold. When he 

ov. PHYSIOL. — 13 



194 



APPLIED PHYSIOLOGY 



makes an extra exertion and becomes short of breath, the an irritates 
the throat and brings on a cough. 

With many, mouth breathing is a habit which can easily be broken 
by attention to the breathing. In others, it is due to a cold, or to ade- 
noid vegetations, or to enlarged tonsils. 

334. The larynx. — In the front side of the lower part 
of the pharynx is the opening of a box called the larynx, 
through which air passes. The larynx is a box of carti- 




A slice from the trachea (x 200). 

a cartilage. b glands in the mucous membrane. 

c lining of epithelial cells. 

d cilia upon the surface of the epithelium. 

lage. Across its upper end are stretched two thin elastic 
bands, the vocal cords, which can be tightened and brought 
near together at will. Air passing between them produces 
a sound called the voice. 

335. The trachea. — From the bottom of the larynx 
there extends downward a tube called the zvindpipe or 
trachea. The trachea is about four and one half inches 
in length and three quarters of an inch in diameter. It 
is composed of a framework of twenty hoops of cartilage, 



THE LUNGS 



195 



bound together with tough connective tissue and lined with 
mucous membrane. 

336. The bronchi. — Within the chest the trachea divides 
into two tubes, the broncJii. Each bronchus divides again 
and again, until the finest 
divisions are about y^^ 
inch in diameter. Like 
the trachea, each bron- 
chus is composed of hoops 
of cartilage lined with 
mucous membrane. 

337. Cilia. — The sur- 
face of the epithelium of 
the mucous membrane of 
most of the nose and 
larynx and the whole of 
the trachea and bronchi 
is covered with micro- 
scopic hairs, the cilia. 
Each cilium is slightly 
curved upward and waves 
continually in a rapid up 
and down motion which 
tends to force dust and 
mucus away from the 
lungs. 

338. The lungs. — The ends of the bronchi are studded 
with numerous cup-shaped depressions called air sacs, each 
about ^^Q- inch in diameter. Upon the inner surface of 
each air sac is a close network of capillary blood tubes. 
The collection of bronchi, air sacs, and blood tubes forms 
two spongy bodies called I?i?i^s. Between the air sacs 
is a thin layer of connective tissue. The lungs can be 




Diagram of trachea and bronchi. 

larynx. b trachea. c bronchi. 

d air sacs of the lung. 



196 



APPLIED PHYSIOLOGY 



Stretched like rubber bags, when air is blown through the 
trachea, and will contract to their former size when the air 
has been let out. 

339. The chest or thorax. — The lungs are covered by 
the ribs, which are hinged to the spinal column behind, 
and to the breastbone in front, so as to form a bony frame- 





Diagram of the air sacs in a man's lung. 

a smallest bronchial tube. 

b a collection of air sacs cut lengthwise. 

c air sacs cut across. 

d connective tissue between the air sacs. 



Diagram of a frog' 
lung. 



work inclosing a cavity called the chest or thorax. The 
floor of the thorax is formed by a muscle called the 
diaphragm, which is attached to the lower border of the 
ribs, and arches upward. It is lined with a smooth and 
shining serous membrane like peritoneum, called the 
pleura. Each lung is covered with pleura also. 

340. Inspiration and expiration. — Muscles connect and 
cover the ribs. They raise the ribs and expand the chest. 
The diaphragm flattens its arch and makes the chest 



THE LUNGS 1 9/ 

deeper. Thus the size of the chest can be increased in 
all directions. When the chest expands, air rushes in 
to distend the lungs. The entrance of air into the lungs 
is called iiispiratioii. At the end of inspiration the 
muscles relax. Then the weight of the parts and the 
elasticity of the distended lung forces out the air. In 
addition, the muscles of the abdomen and arms can be 
made to contract so as to expel the air with greater force. 
Driving out the air from the lungs is called expiration. 

341. Amount of expansion. — In an ordinary inspiration the 
chest becomes from one half an inch to one inch larger around. By 
taking a very deep breatli most people can expand the cliest two or 
three inches. An expansion of four or five incites is exceptional. By 
breathing exercises the expansion can be increased. 

342. Amount of air used in each breath. — After the 
fullest possible inspiration, the lungs contain about 330 
cubic inches of air. After the fullest possible expiration, 
the lungs still contain about 100 cubic inches of air. So it 
is possible, by strong effort, to inhale and exhale about 
230 cubic inches of air. This is called the vital capacity 
of the lungs, and is the breathing power which can be 
used in violent exercise. But in quiet breathing only 
about 3c cubic inches of air are inhaled. This is called 
tidal 21X, By an effort about 100 cubic inches of air can 
be inhaled in addition to the tidal air. This is called the 
complemental air. By a forced expiration, the lungs can 
expel about 100 cubic inches of air more than in quiet 
breathing. This is called the reserve or supplemental air. 
There still will be left 100 cubic inches of air, called 
residual air. 

343. Action of the cilia. — The motion of the cilia creates 
an air current in the smaller bronchi, which mixes the in- 
coming fresh air with that already in the lungs, so that 



198 APPLIED PHYSIOLOGY 

while all the air is not changed with each inspiration, yet 
there is a free mingling of the fresh with the impure air. 
The cilia also intercept particles of dust which the nose 
and pharynx have failed to remove. 

344. Rate of breathing. — In health an inspiration occurs 
with every four heart beats, or about eighteen times each 
minute, but in exercise its rate may be increased to sixty 
or seventy times a minute. A baby breathes about forty 
times a minute. The rate slowly diminishes until, at 
eighteen years of age, it is the same as in a man. 

An inspiration takes about five sixths as long as expira- 
tion, but the regularity and force of both inspiration and 
expiration can be varied indefinitely. Respiration usually 
goes on without a person's knowledge or thought, yet it is 
somewhat under the control of the will in talking, blow- 
ing, and other actions. 

345. Modifications of breathing. — Coughing \^ a forcible expi- 
ration in which the closed vocal cords are suddenly blown open with 
force. 

Sneezing \% a sudden expiration in which air is driven mainly through 
the nose. 

Blowing \^ a long forcible expiration in which air is forced in a steady 
stream through a small opening in the lips. 

Laiighijig and crying are each a succession of short expirations. 
They sound so much alike that it is often impossible to tell which a 
child is doing. 

Sobbing is a succession of short inspirations. 

Hiccoiighing is a single inspiration caused by a sudden contraction of 
the diaphragm. 

Snoring is a sound produced during inspiration by air passing over 
the soft palate. It is usually due to air passing through both the nose 
and the mouth at the same time. 

Gapi7ig or yawning is a long and deep inspiration and expiration 
through the open mouth, while the muscles of the throat are strongly 
contracted. 



THE LUNGS 1 99 

Sighing is a deep inspiration followed by a sudden relaxation of the 
muscles so that the escaping air makes a sound. 

C/iokiHg is a sudden stoppage of the larynx or trachea. When a 
person is choked, he should lie down upon his face with his head 
lowest. Slapping his back will aid in jarring the substance loose. 
If this does not dislodge it, he should be hung head downwards while 
his back is pounded vigorously. In that position the substance may 
fall out, while if he sits upright, it may fall in deeper unless it is coughed 
out. 

Suffocation^ or smothering, is a cessation of breathing caused by 
shutting off the air either partly or wholly. 

Sucking is an inspiratory act, done by depressing the floor of the 
mouth so as to form an empty space into which anything held between 
the lips is forced by the pressure of the air. 

spitting is an expiratory act in which the lips are blown open with 
an explosive noise. It can be done by the mouth alone. 

346. Breathing sounds. — In natural breathing, air rush- 
ing in and out of the lungs produces a low, blowing sound, 
distinct from the sound made by the breathing in the nose 
and throat. The sound of the voice, when transmitted 
through the chest, has a characteristic quality and pro- 
duces a vibration of the chest walls. When the chest is 
struck with the finger, the sound is modified by the reso- 
nant quality of the lungs. All these sounds are changed 
in lung diseases, and give a sure indication of the nature 
and extent of the disease. 

347. Abdominal and thoracic breathing. — When the dia- 
phragm contracts, it forces the abdominal organs down- 
ward, making the abdomen more prominent. Breathing 
by the free use of the diaphragm is called abdominal 
breathing. When the diaphragm remains comparatively 
quiet, the ribs are compelled to move more freely. Breath- 
ing mainly by use of the ribs is called tJioracic breathing. 
In men abdominal breathing is greatest, while in women 
thoracic breathing seems more prominent. 



200 



APPLIED PHYSIOLOGY 



Distention of the stomach and intestine by a full meal, 
or by gas, interferes with the downward movements of 
the diaphragm, and compels a greater extent of thoracic 
breathing. 



Jfh 









.<$' 




Natural form. 



348. Effect of tight lacing. — A person whose waist is 
laced tightly with corsets cannot breathe in the proper 
amount of air, but is short of breath and easily fatigued. 

Tight corsets also compress the liver and other abdomi- 
nal organs. In extreme cases the liver becomes divided 
almost into two parts by the pressure. 



THE LUNGS 



201 



349. The respiratory center. — The movements of the 
chest and diaphragm in breathing are controlled by a 
small part of the brain situated just above the spinal cord, 
and called the respiratory center. When it is destroyed, 







Results of unhealthful dress. 



respiration ceases at once, and no power can arouse it 



Stimulation of the nerves of the body which go to the respiratory 
center may cause it to send out orders for the respiratory muscles to 
act. Thus, suddenly throwing cold water on the chest will cause a 



202 



ArPLTED PHYSIOLOGY 



contraction of the muscles of breathing which lasts for a few seconds, 
so that a person cannot catch his breath. 

A substance sucked into the trachea irritates the nerves which go to 
the respiratory center. The center sends back an order to the respira- 
tory muscles to expel the substance by a forcible blast of air. Thus 
the substance is coughed or sneezed up. 



350. Artificial respiration. — The walls of the chest are 
elastic and quickly return to their natural size when they 

are relieved of 
stress. It is pos- 
sible, therefore, to 
imitate natural 
respiratory move- 
ments upon a man 
who has stopped 
Diagram of artificial respiration, showing inspiration, breathing. This 

The arrows show that the arms are moved outward jg called artificial 
from the sides of the chest. 

respiration. 
By pressing hard upon the chest fifteen or twenty times 
a minute, a great deal of air will be made to pass in and 
out of the chest. 




A more effective 
method is to lay 
the person upon 
his back, with the 
head lowest if pos- 
sible. Standing 
at his head, draw 
each arm out- 
ward and upward, 
in a semicircle, 



f^KP^^^-^-^/o^ 




Diagram of artificial respiration, showing expiration. 

The arrows show that the arms are carried directly for- 
ward until they are pressed hard against the chest. 



away from his body, until they are stretched above his head 
almost in a line with his body. This raises the chest and 



THE LUNGS 203 

produces an inspiration. Then carry the arms directly- 
forward and down and press them forcibly against the 
side of the chest. This produces an expiration. These 
movements should be repeated about fifteen or twenty 
times a minute, or at the rate of natural breathing. 

If an assistant grasps the tongue and pulls it forward 
during each inspiration, it will open the larynx and also 
stimulate the nerves going to the respiratory center. 

Every person should know how to perform artificial 
respiration, for it may be the means of saving a life from 
drowning or from an electric shock. No one should 
hesitate to attempt artificial respiration in these cases, for 
even crude and ignorant attempts will result in the entrance 
of some air and may save a life. 

SUMMARY 

1. The lungs are two organs from which the red blood 

cells obtain oxygen for the use of the cells of the 
body. 

2. Each lung is made of tiny air sacs which communicate 

freely with the air through the windpipe and nose. 

3. Each lung rests upon a curved muscle called the dia- 

pJiragm, and is covered by curved ribs. 

4. When the ribs are lifted or the diaphragm depressed, 

air enters the lungs. This is inspiration. 

5. When the muscles relax, the weight of the parts and 

the elasticity of the lungs drive out some of the air. 
This is expiration. 

6. Inspiration and expiration occur alternately about 

eighteen times a minute. 

7. The movements of the ribs and diaphragm in breath- 

ing are controlled by a small part of the brain just 
above the spinal cord. 



204 APPLIED PHYSIOLOGY 

8. Artificial respiration can be performed by alternately 
pulling the arms above the head and compressing 
them against the chest about twenty times a minute. 

DEMONSTRATIONS 

8i. Each pupil can notice the differenf movements of his own 
breathing. At will he can change from abdominal breathing to thoracic 
breathing, or can use all of the muscles of the chest in taking a very 
deep inspiration. A tape measure passed around the body just under 
the armpits will show how the chest increases in size with each inspira- 
tion and diminishes with expiration. 

82. A small animal should be killed and its chest opened so as to 
show the lungs and heart in place. Notice the shining pleura, and 
that at the back part of the chest it leaves the chest wall and covers 
the lungs. Notice the position of the ribs and diaphragm, and the ar- 
rangement and direction of their muscle fibers. (See demonstration 35.) 

83. In a recently killed cat or dog the diaphragm can be made to 
contract by irritation of the nerve called the phrenic nerve, which con- 
veys orders for motion from the respiratory center to the diaphragm. 
There are two nerves, one of which enters the diaphragm near the 
middle of each side of the arch. Remove the lungs carefully. Then 
the site of the nerve can be recognized by a slight roughness in the 
otherwise smooth pleural covering. Pricking or pinching this point 
will cause a contraction of the diaphragm. (See demonstration 35.) 

84. Kill a frog by placing it in a tight jar with a few drops of chloro- 
form. Open its chest and abdomen. Insert a small pointed glass tube 
into its trachea. The slitlike opening can be found upon the back of 
the tongue. Blow through the tube to inflate the lungs, and at once tie 
a string tightly around their base. Remove the lungs and let them dry. 
Notice the partitions like the cells in a honeycomb, extending a little 
way into the central cavity. Explain that a man^s lung is like a col- 
lection of tiny frog's lungs. (See illustration on page 196.) 

85. Examine a prepared microscopic specimen of a lung and of 
the trachea and bronchi. Notice the ciliated epithelium in the trachea 
and bronchi. Notice that the walls of the air sacs form an irregular 
network inclosing the large spaces of the air sacs. The specimen 
will probably show a small bronchus. Notice its thick walls containing 
some muscular tissue and possibly some cartilage. 



THE LUNGS 205 

86. Show the class how to perform artificial respiration. Have a 
boy lie upon a desk and go through the movements of carrying his 
arms above his head and of pressing them against his side again. Do 
not perform the movements too rapidly and do not press the arms too 
far backward above the head. 

87. The pharynx and palate are puzzling parts to understand, but 
are very simple when shown upon a small animal. With a sharp knife 
and fine saw, divide the head and neck of a small animal through the 
middle of the nose and backbone. Show that the hard palate and the 
soft palate divide the nose from the mouth. Show that the pharynx 
extends upward behind the nose and downward lower than the tongu^. 
Show the position of the tonsils and where adenoid vegetations form. 

88. Cilia can be shown with cells from a frog's mouth. Gently 
scrape its roof, removing a drop of slime with some of the epithelial 
cells. Examine it with the high power of the microscope. The cilia 
will appear as a fringe in rapid motion. (See demonstration 35.) 

REVIEW TOPICS 

1. Define respiration and state its object. 

2. Describe the nose, pharynx, larynx, trachea, bronchi, 

cilia, air sacs, lungs, and pleura. 

3. Describe adenoid vegetations and their effects. 

4. Give the evil effects of month breat/mig. 

5. Describe the chest, ribs, and diaphragm. 

6. Describe inspiration and expiration. 

7. Give the amount of air used in ordinary and in forced 

breathing. 

8. Give the action of the cilia. 

9. Give the rate of breathing, and its variation in laugh- 

ing, sobbing, coughing, hiccoughing, sneezing, gap- 
ing, sighing, and snoring. 

10. Describe the sounds produced by breathing. 

1 1. Describe abdominal and thoracic breathing. 

12. Give the effects of tight lacing. 

13. Describe the respiratory center and its action. 



CHAPTER XXIII 
RESPIRATION OF THE TISSUES 

351. Changes in respired air. — The air is composed of 
atout 80 per cent of nitrogen, 20 per cent of oxygen, and 
y^Q per cent of carbonic acid gas. The nitrogen has no 
effect upon the body, but acts simply by diluting the oxy- 
gen. Air which is ordinarily breathed out from the lungs 
contains 16 per cent of oxygen and 4 per cent of carbonic 
acid gas, while the amount of nitrogen remains unchanged. 
Thus, in breathing, the air gains as much carbonic acid 
gas as it loses oxygen. Expired air is warmer and con- 
tains more watery vapor than inspired air, and sometimes 
contains a trace of a very poisonous organic gas. 

352. Blood changes in the lungs. — Every 100 cubic 
inches of venous blood entering the lungs contain 46 cubic 
inches of carbonic acid gas, and from 8 to 12 cubic inches 
of oxygen gas. As it leaves the lungs the same amount 
of blood contains about 40 cubic inches of carbonic acid 
gas, and 20 cubic inches of oxygen gas, and it has changed 
its shade from the dark red of venous blood to the bright 
red tint of arterial blood. It has also lost a small amount 
of water and some heat. The essential change which 
occurs in the passage of blood through the lungs is the 
exchange of carbonic acid for a corresponding amount of 
oxygen gas. In health, during quiet breathing, the blood 
becomes completely saturated with oxygen. 

353. Affinity of blood for oxygen. — Blood exposed to 

206 



RESPIRATION OF THE TISSUES 



207 



the air takes up 
bri2:ht red color. 



oxygen 
Thus, 



very readily and becomes of a 
blood as it usually flows from 



a slight wound, takes up 
oxygen gas almost im- 
mediately and becomes 
the color of arterial blood, 
and venous blood is sel- 
dom seen. Between the 
dark color of the venous 
blood in the veins of the 
hands, and the brighter 
pink hue of the surround- 
ing skin due to the capil- 
laries, there is a contrast 




Sketch of a thin slice of a lung, showing 
the arrangement of capillaries upon the 
OOd indica- walls of the air sacs (x 50). 



a interior of an air sac. 

b bottom of an air sac covered with capillaries. 

c side of an air sac with capillaries. 



which is a _ 
tion of the usual differ- 
ence between venous and 
arterial blood. 
354. Exchange of oxygen and carbonic acid in the lungs. 

— The blood in the capil- 
laries of the lungs is sepa- 
rated from the air in the 
air sacs by only the thin 
walls of the capillaries. 
Oxygen from the air in 
the air cells passes 
through the capillary 
walls into the blood 
almost as readily as 
though there were no 
walls at all. In the blood 
the oxygen combines with 
the hemoglobin of the red blood cells, and the blood be- 




Capillaries upon the sides of an air sac 

(X200). 



208 



APPLIED PHYSIOLOGV 



comes of a brighter red color as it gains oxygen. Car- 
bonic acid, which was combined with the alkalies of the 
blood plasma, passes through the capillary wall into the 
air of the air sac as easily as the oxygen entered the blood. 

355. The skin and stomach as respiratory organs. — 
Wherever the blood tubes are in contact with the air, 
absorption of oxygen will take place. In the stomach and 
intestine the blood tubes are very near the surface, and 
are in contact with air swallowed with the food. So some 
oxygen will be absorbed and' some carbonic acid gas given 
off. The skin also absorbs oxygen and gives off carbonic 
acid gas. In a frog at least ^ of the respiration is per- 
formed in this way. In man, about ^io ^s much respira- 
tion is carried on by the skin, stomach, and intestine as by 
the lungs. 

356. Respiration of the cells of the body. — After leaving 
the lungs, the blood is distributed through the arteries, 

and enters the capillaries 
of the body. As it enters 
the capillaries it contains 
the same amount of gases 
as when it left the lungs ; 
that is, each lOO cubic 
inches of blood contains 
40 cubic inches of car- 
bonic acid gas and 20 of 
oxygen. As it leaves the 
capillaries, it contains the same amount of the gases as 
the venous blood which enters the lungs; that is, each 100 
cubic inches contains 46 cubic inches of. carbonic acid gas 
and 12 of oxygen. The exchange in the capillaries bal- 
ances the exchange in the lungs. 

When a piece of flesh is put into a dish of blood, oxygen 




Diagram of the respiration of cells. 



RESPIRATION OF THE TISSUES 209 

will leave the red blood cells and combine with the cells 
of the flesh. In a similar way oxygen leaves the red blood 
cells in the capillaries and, passing through their thin walls, 
unites with the cells of the body, producing carbonic acid 
gas, water, and urea. The water and urea go back to the 
blood and are thrown off by the kidneys. The carbonic 
acid gas passes through the capillary wall into the blood 
and unites with the alkalies of the plasma. This goes on in 
every capillary and cell of the body and constitutes the 
real act of respiration. The lungs and red blood cells are 
only devices for carrying oxygen to the deep cells of the 
body. 

357. Oxidation of sugar and fat. — Neither sugar nor fat 
becomes a living part of the cells of the body, but after being absorbed 
both are oxidized at once and furnish about three times as much heat 
and energy as the albumin, which forms a part of the cells. But oxi- 
dation in the body is a living process, and requires the operation of 
living tissues. So it is unlikely that it occurs in the blood stream. As 
sugar is absorbed, the cells of the liver take it into their own substance, 
and probably oxidize it there. In the same way the fat is probably 
taken up by the epithelial cells of the air sacs of the lungs and oxidized. 
In each case the heat is distributed through the whole body by the 
blood. 

358. Respiration a continuous process. — When the 
breath is held, the oxygen in the lungs and that carried 
by the red blood cells is sufficient to supply the body for 
only about half a minute. By the end of that time all the 
blood becomes venous and a great shortness of breath is 
felt. 

Oxygen passes from the lungs through the blood tubes 
to the cells of the body with great rapidity, so that by a 
few deeper breaths enough extra oxygen is taken up by 
the red blood cells to relieve shortness of breath caused 
by their lack of oxygen. 

OV. PHYblOl.. — 14 



2IO APPLIED PHYSIOLOGY 

359. Amount of oxygen used daily. — The amount of 
oxygen used in the body is constantly varying. During 
muscular exertion greater power is required than when the 
body is at rest. To keep up the increased power, more 
oxygen must leave the blood and unite with the muscle 
cells. During sleep less oxygen is needed, but the average 
amount used each day is fairly constant. 

It is a simple example in arithmetic to calculate how much oxygen 
the red blood cells usually carry. 
i8 = no. of respirations per minute. 
30 = no. of cubic inches of air in each inspiration. 
540 = no. of cubic inches of air inspired each minute. 

60 
32400 = no. of cubic inches of air inspired each hour. 

.04 = per cent of air which enters the red blood cells as oxygen. 
1296 = no. of cubic inches of oxygen entering the blood each hour. 
1296-^ 1728 = 0.75 = cubic feet of oxygen entering the blood each hour. 
0.75 

1.2 = ounces weight of a cubic foot of oxygen. 
0.9 = ounces of oxygen entering the blood each hour. 

21.6 = ounces of oxygen entering the blood each day. 

Allowing two or three ounces more for extra exertions, about 25 
ounces of oxygen enter the body each day. This is about the amount 
needed to oxidize the food which a man usually eats. 

The amount of carbonic acid given out is about the same as the 
amount of oxygen taken in, if it is measured in cubic inches. But since 
the carbonic acid is heavier, it amounts to about 30 ounces a day. About 
20 ounces of water are also breathed out each day. 

360. Effect of exercise upon the amount of oxygen 
absorbed. — In quiet breathing each red blood cell is 
loaded with oxygen to its full capacity. During muscular 
exertion the heart beats more forcibly and faster, driving 
the red blood cells more rapidly, and thus, in a given time, 
more oxygen will be carried. Bat when the cells are shot 



RESPIRATION OF THE TISSUES 211 

through the capillaries too rapidly, there is no time for 
either giving or receiving oxygen, and the body may be 
actually starved of oxygen. So the average amount of 
oxygen which the blood can carry is found to be about 
25 ounces daily. 

It is possible to educate the respiratory muscles so that 
during physical exertion they act more regularly and 
strongly. As a result, the lungs are expanded more, and 
a greater area of capiUaries is exposed to the air. The 
heart also may be trained to restrain its violent action, so 
that the blood is not shot through the capillaries of the 
lungs too rapidly to take up oxygen. An athlete trains 
his body so that it can absorb more than 25 ounces of 
oxygen daily, and thus he can put forth a greater 
amount of exertion. Such a person is said to be lo7ig 
ivinded. 

361. Causes of shortness of breath. — The sensation of short- 
ness of breath is usually due to a deficiency of oxygen in the blood 
which circulates through the respiratory center. The blood contains 
too little oxygen when an extra amount of oxygen is used during great 
physical exertion. At first, the heart pumps the blood faster so that it 
carries more oxygen in a given time, but when the blood is pumped 
very rapidly, the red blood cells are shot through the lungs so quickly 
that they cannot obtain the necessary oxygen. When, as in heart dis- 
ease, the blood is pumped too slowly, only a small amount of oxygen will 
be carried through the respiratory center, and there will be continuous 
difliculty in breathing. Shortness of breath is often the first sign of 
heart failure. After severe hemorrhage there are too few red blood 
cells to carry the full amount of oxygen, and so shortness of breath will 
be felt. Death by bleeding is due to suffocation and lack of ox3'gen. 
In the disease called anemia there are too few red blood cells to carry 
oxygen, and so there is shortness of breath on exertion. When the 
larynx or the trachea is compressed or obstructed, as in choking, or 
when the smaller bronchi are filled with mucus, as in bronchitis, oxygen 
is prevented from entering the blood, and the respiratory center (eels a 
great shortness of breath. 



212 APPLIED PHYSIOLOGY 

362. Oxygen inhalations. — Since the red blood cells 
are loaded with oxygen to their full capacity as they leave 
the lungs, they could absorb no more even if it were in- 
haled in a pure form. When there is a shortness of breath 
during disease, pure oxygen is sometimes inhaled to take 
the place of the diluted oxygen of the air. When the lack 
of oxygen is due to a diminished number of red blood 
cells, or if the blood flows too slowly to carry enough oxy- 
gen, inhaling oxygen can do no good, for the blood cells 
leaving the lungs are already loaded with it. The poisons 
of certain diseases may cause the arteries to contract and 
the heart to beat with great force and rapidity. Then the 
blood cells may move so quickly that they have no time to 
take up oxygen from the lungs. Neither rest nor violent 
inspiratory efforts will relieve the resulting shortness of 
breath, but more oxygen may reach the blood cells if it 
is inhaled in a pure form. 

If there is an obstruction to the entrance of air into the 
lungs, more oxygen may pass the obstruction if it is inhaled in 
an undiluted form. When the larynx or trachea is obstructed 
by a membrane in diphtheria, or when the small bronchi are 
filled with mucus, as in bronchitis and pneumonia, then the 
inhalation of pure oxygen may be of great benefit. 

363. Asphyxia. — When the breath is held, a feeling of 
discomfort comes on in about half a minute, which soon 
becomes great distress. If a person is prevented from 
taking a breath, he will become unconscious in a few 
seconds, but will make great inspiratory efforts for a 
minute or more. There will be convulsions, and the face 
will turn purple, for all the blood is venous. Death will 
take place in less than five minutes. This is called 
asphyxia. At any time before death actually takes place 
life can be restored by artificial respiration. 



RESPIRATION OF THE TISSUES 213 

364. Drowning. — Drowning is a form of death by 
asphyxia, but is complicated by the entrance of water into 
the lungs. 

The treatment of drowning is simply to perform artifi- 
cial respiration. In order to do it, it will be necessary to 
remove the water from the lungs. This can be done by 
turning the person upon his face and forcibly compressing 
his back. It will be still better to suspend him head down- 
wards for a few seconds, or standing astride him to raise 
him up and down about twenty times a minute by grasp- 
ing him about the lower part of the chest. This performs 
artificial respiration and lets out the water at the same time. 

The person's limbs should be rubbed vigorously toward 
the heart and kept warm by hot water bottles. No time 
should be lost by carrying him to a building, but artificial 
respiration should be done on the spot. Even if the per- 
son has been in the water half an hour or more, it is 
possible to restore life. 

365. Electric shock. — A shock of electricity kills by 
overwhelming the nervous mechanism which controls the 
heart and lungs. A shocked person is unconscious, and 
apparently lifeless, and yet life may be restored by artifi- 
cial respiration. It should be done at once, and continued 
for a long time if life is not quickly restored. 

366. Effect of alcohol upon the lungs. — Alcohol partially 
paralyzes the arteries of the body so that they dilate and 
permit a larger quantity of blood to pass through. Thus, 
the capillaries of the lungs may be distended with the rest. 
Then they may partly fill the air sacs so that less air can 
enter. If the distension continues for some time, the walls 
of the capillaries may thicken so that oxygen will pass 
through them less readily. The walls of the air sacs 
themselves may become thickened, and the exchange of 



214 APPLIED PHYSIOLOGY 

oxygen and carbonic acid impeded. This effect may be 
produced by continuous moderate drinking. 

367. Alcohol interferes with the respiration of the cells. — 
Alcohol is quickly absorbed from the stomach and intes- 
tine and as quickly disappears. After it is taken, little 
or no alcohol, or any substance like alcohol, or any sub- 
stance containing so little oxygen as alcohol, can be found 
in any waste of the body. Hence the inference is that it 
must be oxidized, although the exact point and the manner 
of its oxidation may not be known. But the evidence for 
its oxidation is the same as that for the oxidation of sugar. 

Every ounce of alcohol requires nearly two ounces of 
oxygen to oxidize it fully. Taking twenty-five ounces of 
oxygen gas as the amount used in a day, there will be only 
one ounce used in an hour. So to oxidize an ounce of 
alcohol takes an amount of oxygen equal to the whole 
supply of the body for two hours. Three or four drinks 
of whisky contain this ounce of alcohol. If this amount 
is drunk, there will soon be a lessened action and a nar- 
cotic effect throughout the body, due mainly to the lack 
of oxygen. A noticeable degree of uncertain action is 
called intoxication. 

Using alcohol in the body is like burning kerosene in 
a coal stove. By taking great care a little kerosene can 
be made to give out some heat from the stove, but the 
operation is dangerous. Some people seem to oxidize 
alcohol within the body with but little harm ; but they 
run great risks of doing themselves harm, and the result 
is not nearly so good as if they had used proper food. 

368. Poisons produced by alcohol. — When too little oxy- 
gen enters the draft of the stove, the wood is burned im.per- 
fectly, and there are clouds of smoke and irritating gases. 
So, if oxygen goes to the alcohol and too little reaches 



RESPIRATION OF THE TISSUES 215 

the cells, instead of carbonic acid gas, and water, and urea 
being formed, there are other products, some of which are 
exceedingly poisonous and which the kidneys handle with 
difficulty. The poisons retained in the circulation never 
fail to produce their poisonous effects, as shown by head- 
aches, clouded brain, pain, and weakness of the body. 
The word intoxication means, ** in a state of poisoning." 
These poisons gradually accumulate as the alcohol takes 
oxygen from the cells. The worst effects come last, when 
the brain is too benumbed to judge fairly of their harm. 
It is not true that alcohol in a small amount is beneficial. 
A little is too much, if it takes oxygen which would 
otherwise be available to oxidize wholesome food. 

369. Effects of tobacco. — Tobacco smoke contains the 
same kind of poisons as the tobacco, with other irritating 
substances added. It is usually sucked into the mouth 
and at once blown out again, but cigarette smoke is com- 
monly drawn into the lungs and afterwards blown out 
through the nose. It is irritating to the throat, causing 
a cough and rendering it more liable to inflammation. If 
inhaled into the bronchi, it produces still greater irritation, 
and the vaporized nicotine is more readily absorbed as the 
smoke is inhaled the more deeply. Cigarettes contain the 
same poisons as other forms of tobacco, and often contain 
other poisons which are added to flavor them. 

370. Respiration in birds. — The lungs of all land ani- 
mals are like man's lungs, and the process of respiration 
is the same. The lungs of birds are fixed in the upper 
part of the thorax, and in addition they are provided with 
two smooth bags, each somewhat larger than the lung. 
Each bag connects with the air sacs of the lung, and also 
with the interior of the larger bones. Respiration can 
occur in the bags and bones as well as in the lungs. 



2l6 



APPLIED PHYSIOLOGY 




The air bags are expanded with air during flight, and 
thus the body is made hghter in proportion to its size, 
in order that the bird may fly more easily. 

371. Respiration in amphibious animals. — Some water 
animals, like the porpoise and whale, possess lungs like 

land animals, and are com'pelled 

to come to the surface of the 

water in order to breathe, but 

fish have a special apparatus so 

that they can use the oxygen 

which is dissolved in water. On 
Gills of a fish. g^^j^ g-^g Qf ^ l^gl^.g j^g^^ -g ^ g|.^_ 

like opening reaching from the interior of the mouth to 
the surface of the body. In each opening are four half 
circles of limber bone. From the back of each circle a 
row of thin fingerlike plumes projects, so that it looks 
like a red feather with plumes only on one side. These 
half circles are the gills. Each plume contains a blood 
tube which is separated from the water by a very thin 
wall. The fish forces the water through his mouth and 
out between the gills, and the oxygen contained in it 
readily passes through the thin wall of the blood vessel 
into the red blood cells. 

372. Respiration in a frog. — A frog in the tadpole 
form is provided with gills which project into the water 
from its neck, but when it becomes a perfect frog the 
gills disappear and lungs are formed. But the frog's skin 
is able to absorb oxygen and to give off carbonic acid 
gas about one eighth as rapidly as the lungs. 

373. Respiration in insects. — In insects from three to 
nine tubes extend into each side of the abdomen and 
divide into small branches, but do not communicate with 
any cavity. The fluid which answers for the insect's 



1 



RESPIRATION OF THE TISSUES 21^ 

blood comes in contact with the surface of the tubes and 
absorbs oxygen from the air in them. As they possess no 
hemoglobin or red blood cells, oxygen is simply dissolved 
in the blood ; but owing to the small size of their bodies, 
this is sufficient for their use. 

374. Respiration in shellfish. — Shellfish, such as oysters 
and clams, have gills hke fringes along their front edges. 
The gills are covered with cilia which cause currents of 
water bearing food and air to flow through the shell. 

375. Respiration in plants. — A plant also breathes. 
While it uses heat from the sun in the manufacture of 
starch from the carbonic acid gas and water, yet for its 
own movements it requires a production of heat within 
itself. In order to climb a pole and unfold its flowers, a 
vine requires power which is furnished by the oxidation of 
its own substance. At the height of the flowering season 
the temperature of the plant is raised slightly above that 
of the surrounding atmosphere, and carbonic acid gas is 
given off. In every case the heat and power is furnished 
by oxidation of some of the plant's own substance, but the 
amount of carbonic acid gas given off is insignificant in 
comparison with the amount of carbonic acid gas which 
the plant uses as food. A little oxygen is absorbed by 
the leaves, but it is small in amount compared with what 
is given off by the plant. 

SUMMARY 

1. As blood passes through the capillaries of the lungs it 

gives carbonic acid gas to the air and takes about 
the same amount of oxygen from the air. 

2. As blood passes through the capillaries of the body it 

gives up oxygen to the cells and takes carbonic acid 
gas from the cells. 



2l8 APPLIED PHYSIOLOGY 

3. The exchange in the two sets of capillaries balances. 

4. Within the living cells the oxygen unites with the 

albumin, fat, and sugar, producing carbonic acid 
gas, water, and urea. 

5. About twenty-five ounces of oxygen are used daily in 

oxidizing the body. 

6. When not enough oxygen is present within the body, 

there is a shortness of breath. 

7. Alcohol often causes distension and thickening of the 

capillaries and of the walls of the air sacs, so that 
oxygen passes through them less readily. 

8. The alcohol of three or four strong drinks of liquor 

uses as much oxygen as would supply the whole 
body for two hours. 

9. As a result of taking oxygen from the cells of the 

body, the cells act in an uncertain manner, which is 
called intoxication. 

10. Tobacco smoke irritates the air passages. It contains 

nicotine, which can enter and poison the body. 

11. All kinds of animals and plants breathe in oxygen 

and give off carbonic acid gas. 

DEMONSTRATIONS 

89. With a glass tube, blow air through some limewater, and notice 
that it grows milky, showing the presence of carbonic acid gas. Breathe 
upon a cold glass and notice that moisture collects from the breath. 
Call attention to the fact that bad odors in the breath are due to de- 
cayed teeth, a coated tongue, or foul stomach, or possibly to a dirty nose. 

90. The change in color from venous to arterial blood can be illus- 
trated by cutting into a thick slice of beef. At first the cut surface is 
dark and purplish, and of the color of venous blood. But in a few sec- 
onds the blood in the meat absorbs oxygen from the air and becomes 
bright red in color like arterial blood. 

91. With two needles tease apart a bit of gill from a shellfish and 
examine it with the microscope for the waving cilia. 



RESPIRATION OF THE TISSUES 219 

92. Show a fish's gills and if possible a tadpole's also. "Wrig- 
glers,'' or the young of mosquitoes, can be found in a rain barrel, and 
are very interesting. At the tail there is a tuft of stiff hairs through 
which it breathes. They wriggle about in the water and at intervals 
come to the surface and thrust out the tuft of hairs so as to get a supply 
of oxygen. 

REVIEW TOPICS 

1. Give the changes occurring in the air within the lungs. 

2. Give the changes which occur in the blood within the 

lungs. 

3. Show that the blood carries oxygen. 

4. Show that the skin and stomach are respiratory organs. 

5. Show that the cells of the body take oxygen and give 

off carbonic acid gas. 

6. Show that the blood carries carbonic acid gas. 

7. Show that respiration is a rapid and continuous 

process. 

8. Calculate how much oxygen is used daily and how 

much carbonic acid gas is given off. 

9. Show why a person becomes long winded by training. 

10. Give some causes of shortness of breath. 

11. Tell when and why inhalations of pure oxygen are of 

benefit. 

12. Give the effects of alcohol upon the walls of the air 

sacs. 

13. Show how alcohol affects the respiration of the cells. 

14. Show how alcohol causes poisons to develop within the 

body. 

15. Give the effects of tobacco upon the air passages. 

16. Show how respiration is modified in birds, in fish, in 

frogs, in insects, and in shellfish. 

17. Explain the respiration of plants. 



CHAPTER XXIV 
THE AIR AND VENTILATION 

376. Composition of air. — Every lOO parts of air arc 
composed of about 20 parts of oxygen and 80 parts of 
nitrogen : ^^q per cent of the air is carbonic acid gas. 
Air contains water in varying amount. Some dust par- 
ticles are always floating about, and also a few living 
germs of plants like those producing mold and yeast. 
These substances are found in all air, and none are 
harmful. 

377. Ozone in the air. — There is a form of oxygen called 
ozone which is much more active than common oxygen. It 
can be made by passing a strong current of electricity 
through a tube of oxygen. During thunderstorms some is 
formed, which imparts a peculiar odor and exhilarating 
property to the air. Some is formed in pine forests, and 
to it the beneficial effeots of the forests upon consumptives 
may be due. It is never found in any great amount in 
the air. 

378. Argon. — It was discovered in 1894 that the part 
of the air supposed to be pure nitrogen contains a gas 
hitherto unknown, to which the name argon has been given. 
One per cent of the air is argon. Like nitrogen, it cannot 
be made to unite with any substance directly from the air, 
and so both act simply to dilute the oxygen. But, unlike 
nitrogen, it does not form a chemical combination with 
anything at all, but is always found simply mixed with the 



THE AIR AND VENTILATION 221 

air, or with a few other substances. Its discovery has not 
modified our ideas of the physiological effects of the air. 

379. Dust in the lungs. — If the dust in the air is small in 
amount, it adheres to the moist surface of the nose and pharynx, and 
does not enter the trachea. If some enters the trachea, it becomes 
entangled in the cilia of the epithelial cells and is forced back towards 
the mouth and then coughed out. If the air is very dusty, some dust 
will enter the air sacs. Instead of letting it remain to fill up the lungs, 
nature has given the lymphatics the power to take the dust particles 
and to carry them to the nearest lympli nodes, where they are deposited 
and remain harmless. 

380. Occupation diseases. — Even though the lymph nodes 
take care of inhaled dust, after a while the continuous irritation of the 
hard particles injures the delicate lining of the bronchi and air sacs, 
and causes bronchitis or asthma or pneumonia. Tool grinders are 
especially liable to the trouble, for the fine particles of stone and steel 
which fly oif in their work and are inhaled, cannot be taken up by the 
lymphatics. Potters, miners, flax workers, and pearl button makers 
are all subject to lung troubles to a greater degree than workers in a 
dustless atmosphere. Those who work with quicksilver or phosphorus 
are liable to inhale the fumes and be severely poisoned. 

381. Amount of oxygen needed to support life. — When 
inspired air contains less than 20 per cent of oxygen, a 
shortness of breath comes on, which is in proportion 
to the lack of oxygen. A candle will not burn in air 
containing less than 17 per cent of oxygen, while air 
containing only 15 per cent of oxygen will support life, 
but there will be great shortness of breath. In old wells 
and cellars oxygen is often replaced by carbonic acid gas, 
and men have been suffocated in them. A simple test of 
the safety of entering them is to lower a lighted candle 
into the suspected place. If it burns, there is surely 
enough oxygen to support respiration. When the amount 
of oxygen is diminished to ten per cent, animals die in a 
few moments with all the symptoms of suffocation. 



222 APPLIED PHYSIOI-OGY 

382. Rarefied air. — Every square inch of surface, in- 
cluding that of the body, sustains a weight of fifteen 
pounds of air, but it is balanced by an equal pressure of 
air inside the body, in the lungs and stomach and other 
cavities, and so it is not felt. At high elevations there is less 
atmosphere pressing from above, and so the air expands 
and becomes lighter. Then a lung full of air will contain 
less oxygen. At a height of three and a half miles the air 
is only one half as dense as at the surface of the earth, 
and at the height of five miles it is almost impossible to 
breathe enough oxygen to sustain life. The lessened 
pressure upon the body disturbs the flow of blood, espe- 
cially in the brain, and produces dizziness and fainting. 

In mountainous regions the air is lighter and holds less 
moisture than in lower regions. It is also purer, for it is 
removed from the contamination of cities which crowd the 
lower waterways. So those regions are favorable for those 
suffering with lung diseases such as consumption. Proba- 
bly a still greater benefit is derived from the respiratory 
exercises and the full expansion of the lungs which are 
necessary in order to obtain sufficient oxygen. 

383. Effect of increased pressure of air. — In working 
under water in laying deep foundations for buildings, a 
large box called a caisson is sunk to the bottom, and into it 
air is forced so as to keep out the water. Men work within 
the caisson subjected to double or triple the natural pres- 
sure of air. Although more air is inspired with each breath, 
the blood does not seem to take up more oxygen than usual ; 
but the increased pressure of air upon the arteries and veins 
produces great disturbances of the circulation. It is impos- 
sible to remain in the caisson longer than an hour or two 
at a time. In leaving the caisson, the air pressure must 
be diminished as slowly as on entering, so as to permit 



THE AIR AND VENTILATION 223 

the liberated gases tO expand slowly. The ear drums 
could be easily ruptured by a quick change in pressure. 
Sometimes the pressure causes a severe injury of the 
spinal cord. 

384. Effects of carbonic acid gas. — Carbonic acid gas 
itself has very little harmful effect upon the body. When 
air containing one fourth its bulk of carbonic acid gas is 
inhaled, the air sacs soon contain more of the gas than 
is found in the blood. Then carbonic acid gas is no longer 
given off, but remains in the blood and air sacs, and pre- 
vents the entrance of oxygen. Shortness of breath, uncon- 
sciousness, and death soon occur, caused mainly by the 
displacement of the oxygen. Carbonic acid has been used 
to produce insensibility during surgical operations but its 
effects cannot be controlled, and its use is unsafe. 

When many persons are confined in a small room, the 
oxygen is speedily used up, and carbonic acid gas takes its 
place. When the amount of oxygen is diminished to ten 
per cent, death will occur, caused rather by the lack of 
oxygen than by the presence of the carbonic acid gas or 
other substances in the expired air. But discomfort will 
be felt long before the oxygen is diminished to an appre- 
ciable degree. 

385. Foul air. — Besides the carbonic acid gas, the ex- 
pired air contains a greater or less quantity of water and 
of foul-smelling vapors. Odors are constantly given off 
also by the skin of the most cleanly persons. In the air 
of a closed room in which several people have been for 
some time, there is a characteristic odor which belongs to 
man, just as certain odors are peculiar to different lower 
animals. These odors are very oppressive. They cause 
sickness in sensitive persons mainly because of their 
unpleasantness. This effect passes off when pure air is 



224 APPLIED PHYSIOLOGY 

breathed. The heat of a closed room greatly intensifies 
the effect of the foul air. 

386. Cause of bad effects of foul air. — No one thing can 

be found in stufify air to account for all the bad feelings which it pro- 
duces. The diminution of oxygen is too sHght to produce noticeable 
effects, but the combination of heat and foul odors is very oppressive 
to persons not accustomed to them, while the carbonic acid gas tends 
to cause drowsiness and dullness of mind. Those who live in a foul 
atmosphere continually are usually too poor to buy nourishing food, 
and too busy to take exercise in the open air, and, moreover, are 
greatly overworked. These causes produce even more ill health than 
the foul air. 

387. Bad odors. — Decaying matter gives olT bad odors. Many 
animals and vegetables have an offensive smell, and in many manu- 
factures foul odors are continually poured into the air. These odors 
in the air are seldom harmful, yet the source of the odors is usually 
dangerous to health, and the odors are given off as a warning. It 
is nearly always true, that harmful things have an offensive smell and 
taste. So a bad odor reveals a decaying body which might poison a 
well, or a disease which might be communicated to others. 

Since odors are only signs, the danger is not past if only the odor 
is destroyed. Ammonia, carbolic acid, or perfumery may mask the 
odor, but they only obscure the source of danger. 

388. Sewer gas. — Sewer gas is exceptionally offensive 
and penetrating. The odor is not especially harmful, but 
disease germs which are emptied into the sewer from sick 
rooms are easily carried with the gas. Usually the strong 
odor betray^ the leak in the pipes before the germs have 
gained an entrance. 

389. Cellar air. — Cellars are apt to be closed, so that little 
fresh air and light can enter. Decaying vegetables and other sub- 
stances may accumulate in the corners. This makes a breeding place 
for disease germs, which may be carried up through the floors into 
living rooms above. A cellar should be kept dry, clean, and well 
aired. 



THE AIR AND VENTILATION 22$ 

390. Malaria. — Malaria, chills and fever, fever and 
ague, or intermittent fever, as the disease is variously 
called, is caused by germs which come from stagnant 
water or wet earth. The air in low localities within a few 
rods of a marsh may be full of the germs, while a hill in 
its midst may" be free. 

Drainage of infected ponds, or sleeping in the upper 
stories of houses, or removing to a hill overlooking the 
marsh, will probably overcome the infection. Newly 
turned earth or damp cellars may also be breeding places 
for the disease. 

391. Night air. — There is a popular belief that during the night 
the air contains some harmful substance which disappears during the 
day. But the air of the early evening, which is supposed to be the 
worst air of the day, has been purified by hours of sunshine, while 
the air of early morning, which is supposed to be the best of the day, 
has been exposed to hours of the noxious influences of darkness. So 
the belief is a contradiction in itself. 

392. Contamination of air by fire and light. — In addi- 
tion to the impurities produced by breathing, the air of 
inhabited rooms is further rendered impure by fires and 
lamps. A tallow candle will consume half as much oxy- 
gen in a given time as a man. A lamp burning a pint of 
oil in an evening uses as much oxygen, and gives off as 
much carbonic acid, as a man gives off during a whole 
day. A stove uses an immense amount of oxygen, but the 
gases pass up the chimney. Candles and lamps often 
pour bad-smelling gases into the air. 

393. Coal gas. — When coal is heated, it gives off a gas called 
carbofiic oxide. Carbonic oxide is the main part of illuminating gas, 
and in a stove, burns with a blue flame. It is extremely poisbnous 
when breathed. It unites with the hemoglobin of the red blood cells 
and destroys their power of carrying oxygen. Gas from a smoking 

OV. PHYSIOL. — I :; 



226 APPLIED PHYSIOLOGY 

coal stove or a leaking gas pipe may smotlier a whole family while they 
are asleep. 

In treating a case of poisoning by gas, an abundance of fresh air 
should be admitted, and artificial respiration should be performed. 

394. Germs of disease in foul air. — Disease germs may 
be breathed into the air. If the air of ^^oom smells 
stuffy, it is a hint that the germs as well as the stuffy 
odors may be accumulating. Lung diseases are especially 
frequent among those who work in close rooms. The 
germs of measles, scarlet fever, and all other *' catching" 
diseases, are also likely to accumulate in a close room. 
Sick persons often breathe out the germs of disease, which 
may reenter the body and continue the disease. More- 
over, every discomfort retards recovery, so in sick rooms 
and hospitals a continuous supply of fresh air is especially 
necessary, while in every room the air should be changed 
often enough to prevent the stuffy odor from developing. 

395. Consumption. — Tuberculosis of the lungs, or consumption, 
is an infectious disease, caused by the growth of living germs within 
the lungs. A person suffering with consumption is continually giving 
off the germs in the secretions from his air passages. His handker- 
chief contains millions of them. While moist they remain on the 
handkerchief or clothes, but when dry they may float through the air, 
and when inhaled may produce the disease. A consumptive is always 
a menace to other occupants of a room, especially if he does not exercise 
great care with the secretions from his nose and mouth. 

396. Ventilation. — Continually replacing the impure air 
of a room with fresh air is ventilation. Nowadays, with 
air-tight rooms and closed stoves, openings need to be pro- 
vided for the exchange of air. When, by breathing, the 
quantity of carbonic acid gas in the air is increased by one 
half its natural amount, other substances have also en- 
tered the air, so that it begins to be stuffy. When the 



THE AIR AND VENTILATION 22'J 

quantity of carbonic acid gas is doubled, the air is mark- 
edly oppressive. If the carbonic acid gas is increased to 
three times its natural amount, the air is too oppressive for 
comfort, and may contain enough germs of disease to be 
dangerous to health. 

397. Computation of amount of fresh air. — About ^^^ P^^ 

cent of fresh air is carbonic acid gas. Wlien -^^^ per cent more of 
carbonic acid gas has been added to the air, the air begins to be stuffy 
and unfit for use. Suppose there is an air-tight room twenty feet square, 
and ten feet in height, and in it one man is living ; the room will con- 
tain 4000 cubic feet, yl^ per cent of 4000 cubic feet is 3% of a cubic 
foot, which is nearly the average amount of carbonic acid gas breathed 
out by the man each hour. Thus in an hour a man renders 4000 cubic 
feet of fresh air stuff}'. In reckoning the amount of fresh air to be 
admitted to rooms, 4000 cubic feet per hour is the smallest amount 
which can be safely allowed. Therefore, if only one person breathes 
the air of a room twenty feet square, and ten feet high, the air needs 
to be wholly renewed each hour, and yet it contains enough oxygen to 
last a week. Fresh air is needed when the air of a room smells stuffy 
to a person coming from pure air. 

398. Natural ventilation. — When air is heated it ex- 
pands so as to fill more space. While a cubic foot of air 
at a temperature of 32° F. weighs about 1.2 ounces, at 
80° F. it weighs about i.i ounces. So heated air, being 
lighter, tends to rise. The air is slightly warmed in 
breathing, and so tends to rise to the ceiling, while the 
cool air which enters the room remains near the floor. 
So the floor is usually cooler than the ceiling. If an 
opening is made near the ceiling, and another near the 
floor, the warm air of the breath will naturally pass out at 
the upper opening, and the cool fresh air will enter the 
lower opening. If only a few persons are in a room, 
the openings about windows and doors may be sufficient 
without special ventilation. If many persons are together 



228 



APPLIED PHYSIOLOGY 



in a room, the natural cracks and openings are not suffi- 
cient, but other openings must be made. 

399. Methods of ventilation. — In ventilation a per- 
ceptible current of air must be avoided, for many people 
easily take cold when a single part of the body is cooled 




Diagram of the natural ventilation of a room. 

The arrows indicate the direction of the air currents. 

as by a draft. The air of a room can be changed only 
three times an hour without producing noticeable drafts 
throughout the room. 

Many devices have been used to secure an even distribution of the 
incoming fresh air. The simplest is to lower the upper window sash. 
Warm air will pass out above the upper sash, while the cooler fresh air 
will enter between the two sashes, and will be given an upward direc- 



THE AIR AND VENTILATION 229 

tion toward the warmer air of the ceiling. There it wdll become warm, 
and finally will spread through the room like a gentle shower, instead 
of in a rushing stream. 

A modification of the same idea is to raise the lower sash a few inches 
and insert a narrow board in the lower opening, so that a space is left 
between the sashes for the entrance of fresh air. The opening for fresh 
air may be through the floor under the stove, and thus the air will be 
heated as it enters the room. An open fireplace produces an upward 
current of air. An opening into the chimney flue near the ceiling will 
carry off much of the foul air. 

In many churches a small part of the window, is hinged so that its 
top can incline inward. If the window is placed about two thirds of 
the way between the floor and ceiling, the warm air will pass out above 
the window, while the cool, fresh air will enter below it. The inclina- 
tion of the window will cause the air to flow toward the ceiling at first, 
where it will be warmed and scattered so that it cannot produce drafts 
upon the heads of the listeners. The addition of an opening in the 
center of the ceiling for the escape of the warm air forms an efficient 
mode of ventilation. 

Hot air registers both heat and ventilate a room, if care is taken to 
admit fresh air to the pipes. The hot air passes up from the furnace 
because it is lighter. An opening in the window or into the chimney 
is needed to allow the air of the room to escape, so that the w^arm fresh 
air can enter. 

Since on a cold day the air inside a room is much warmer than the 
air outside, a current of air will rush through every crack, so that 
good ventilation will be secured by a very small opening. Since on a 
warm summer's day the air inside and outside is nearly of the same 
temperature, large openings are necessary to effect the change of air. 

400. Forced ventilation. — In large buildings, such as factories 
and theaters, warm fresh air is forced into the rooms by rotary fans, and 
the impure air escapes through openings in the ceiling. Thus the 
amount of heat and air admitted can be exactly regulated. 

Another way of ventilating large houses is to suck out the impure 
air by rotary fans, while fresh warm air is adinitted through small open- 
ings near the floor, thus preventing drafts. This method is being 
adopted in large buildings to the exclusion of other methods. 

401. Filtration of air. — In forced ventilation the air is con- 
ducted through a large box, which has partitions arranged so as to 



230 APPLIED PHYSIOLOGY 

break the air current and allow the dust to settle. In some, the air is 
passed through a layer of cotton. Cold air contains less moisture than 
warm air, and unless the air is given more moisture before it is sent to 
the rooms, it will be very dry. So a pan of water should always be 
kept inside the air box of a furnace. 

402. Schoolroom ventilation. — Children are especially 
susceptible to unhealthful surroundings, and the air of 
a schoolroom, in which they spend the greater part of the 
day, should be kept pure. Pure air means clearer brains 
and better lessons, and may determine whether or not a 
child shall gain a sufficient knowledge to assure his suc- 
cess in life. In every half day of school it is well to allow 
a short recess in which windows and doors can be thrown 
wide open and the pupils sent out to get deep breaths of 
oxygen during play. 

The upper sashes of all the windows on the side of the 
schoolroom away from the wind can be kept open a space 
so as to produce a gentle outward current of foul air. 

If the upper sashes cannot be lowered, the lower one 
can be raised and a board inserted under it so that the 
only opening left is between the two sashes. 

If registers or special means of ventilation are provided, 
they should be watched and regulated according to the 
needs of the air. 

403. Purification of the atmosphere. — Although it is con- 
tinually receiving impurities, the atmosphere as a whole never becomes 
foul, for the process of purification never ceases. First, the wind scat- 
ters the impurities to a height miles above our heads and over the seas 
to arctic and uninhabited regions, and thus dilutes the impurities. 
Second, rain washes out dust and germs and soot, and foul gases, and 
carries them into the earth. Third, sunlight destroys living germs 
floating in the air, and dries up stagnant sources of impurities. Fourth, 
plants, both on land and in the sea, absorb carbonic acid gas and 
restore the oxygen to the air. By these means the composition of the 
air is kept always the same. 



THE AIR AND VENTILATION 23 1 

SUMMARY 

1. Air is essentially oxygen diluted with four times its 

volume of nitrogen. 

2. When the amount of oxygen is diminished there is 

shortness of breath. 

3. Exhaled carbonic acid gas is not poisonous in itself, 

but if present in great amounts it may keep oxygen 
out of the lungs. 

4. Foul-smelling vapors, carbonic acid gas, moisture, and 

the contamination by fire and lights make the air of 
crowded rooms oppressive. 

5. Coal gas inhaled may unite with the hemoglobin in the 

red blood cells so that they will not carry oxygen. 

6. The main thing to be feared in close air of crowded 

rooms is the disease germs which may be breathed 
into it. 

7. The air of a room should be changed often enough to 

allow 4000 cubic feet of fresh air to each person 
each hour. 

8. Breathed air is warm, and tends to rise and pass out of 

cracks and openings in the upper part of the rooms, 
while cold, fresh air enters by lower openings. 

9. In large buildings the foul air is either forced or 

drawn out by rotary fans, and fresh warmed air 
enters to take its place. 
10. The atmosphere is purified by winds, rain, sunlight, 
and plants. 

DEMONSTRATIONS 

93. The harmlessness of carbonic acid gas can be illustrated by 
soda water, which is water in which a large amount of the gas is held 
undcv pressure. Open a bottle and inhale the liberated gas. Notice 
its pungent odor and taste. 



232 APPLIED PHYSIOLOGY 

94. Hold a candle or lighted match near each crack of the room and 
notice that usually the flame is blown towards the inside from cracks 
near the floor, while it is blown outward in cracks higher up. 

95. Clap two blackboard erasers together to make a small cloud of 
dust, and watch the movements of the particles in a ray of sunlight, so 
as to detect the direction of the air currents in the room. 

96. Show methods of ventilation by lowering the upper sash ; by 
raising the lower and inserting a board in the opening. Show and 
explain the methods of ventilation adopted in the school. 

REVIEW TOPICS 

1. Give the composition of the air. 

2. Describe ozone ; argon ; nature's method of removing 

dust from inspired air ; and the dangers of inhaUng 
dust in certain trades. 

3. Tell how much oxygen is needed in the air to sustain 

life, and give a simple test to determine whether 
sufficient is present. 

4. Give the effects of rarefied air, and air under increased 

pressure. 

5. Give the effects of carbonic acid gas. 

6. Describe foul air and its effects. 

7. Discuss the meaning and the effects of bad odors ; of 

sewer gas ; of night air ; and of cellar air. 

8. Describe malaria. 

9. Show how fire and lights contaminate the air. 

10. Describe coal gas poisoning. 

11. Show that foul air may contain disease germs. 

12. Calculate how much fresh air should be admitted into 

a given room for a given number of persons. 

13. Describe how ventilation naturally goes on, and tell 

some ways of assisting nature in ventilation. 

14. Tell how a schoolroom may be ventilated. 

15. Tell how the atmosphere is purified. 



CHAPTER XXV 

HEAT AND CLOTHING 

404. Temperature of the body. — During health a man's 
body has a temperature of 98^° F., which does not change 
either upon the warmest day in summer or the coldest day 
in winter. The body is warmed by the oxidation of its 
own cells and of digested food. 

405. Change of heat to energy. — The power which the 
body puts forth in performing work is derived from the 
heat of oxidation. The work of the heart requires the 
use of y^g of all the heat produced in the body ; the respi- 
ration requires g^ ; digestion and absorption require a 
smaller amount. An ordinary day's work requires -f^ of 
the total amount of heat. So nearly three fourths of all 
the heat produced is used simply to heat the body. 

406. Uniformity of temperature. — In some parts of the body 

oxidation is many times more active than in others. Probably most 
of the sugar is oxidized in the liver, and most of the fat in the lungs. 
As fast as heat is developed it is carried all-over the body by the blood, 
so that there is scarcely half a degree's difference between the tem- 
perature in any two parts. Only the surface of the skin is cooler 
because it comes in contact with cooler air. 

407. Fever. — When the temperature of the body is 
raised only a degree there is a feeling of warmth and dis- 
comfort, which is called 2i fever. The discomfort is worse 
as the temperature is higher. A temperature of 104 de- 
grees is a high fever, and if continued may cause death. 

233 



234 APPLIED PHYSIOLOGY 

408. Sensation of heat and cold. — If the temperature is 
lowered only a degree, there is a feeling of coldness called 
a chill. A chill is a recognized sign of beginning illness. 
The ordinary feeling of heat or cold is due to the state of 
the nerves of the skin, whose special duty is to conduct 
sensations of temperature. These nerves are so abundant 
in the skin that their sensations overpower the sensations 
of the rest of the nerves of the body. If the skin is warm, 
the whole body feels warm ; while if the skin is cold, the 
whole body feels cold. 

409. Chills during a fever. — It often happens during a fever 
that the blood goes to deeper parts, leaving the skin pale and without 
its usual supply of heat, and so the whole body feels cold, and the per- 
son has a chill, although the temperature of the body may be raised 
several degrees. 

In severe sickness the heart is sometimes too weak to pump the 
blood to the skin, and so it feels cold, although the temperature of the 
inside of the body may be raised several degrees. This condition is 
often called inward fever. On the other hand, the body may be cold, 
and yet if the blood is brought to the surface, the person will feel warm. 

410. Regulation of the heat produced. — The amount of 
heat produced in the same body varies widely at different 
times, and some persons always produce many times as 
much as do others. So in order to keep the temperature 
constant, heat must be given off at one time and saved at 
another. Nature regulates the temperature of the body 
by varying both the amount produced and the amount 
given off. The production of heat depends partly upon 
the amount of food. In summer man naturally eats less 
than in winter. Inhabitants of arctic regions eat large 
quantities of fat, the oxidation of which produces a large 
amount of heat, while the inhabitants of hot climates 
naturally avoid fat. 



HEAT AND CLOTHING 235 

The production of heat also depends upon the amount 
of oxygen taken into the body. In work, deeper inspira- 
tions are* taken, and more oxygen reaches the cells, and 
thus exercise warms the body. 

411. Regulation of the heat given off. — Nature also 
regulates the amount of heat given off. The body loses 
some heat through the breath, and more by contact with 
the cool air. When the temperature of the inside of the 
body is raised, the blood tubes of the skin dilate, so that 
more blood comes in contact with the air. If the tempera- 
ture falls slightly below the natural point, the blood tubes 
of the skin contract, so that less blood comes to the sur- 
face, and more heat is retained until the temperature rises 
to the natural point again. A change of temperature too 
small to be felt will produce these changes in the blood 
tubes of the skin. 

412. Effects of tight bands. — When the circulation is hindered 
so that less blood enters any part of the body, its temperature falls. A 
finger whose veins are compressed by a tight string becomes percepti- 
bly cooler in less than a minute. Garters often cause cold feet in the 
same way. Compression of the waist may cause the whole body to feel 
cold. 

413. Effects of perspiration. — Sometimes men work in 
air which is hotter than their bodies. Then instead of 
giving, they receive heat. In order to keep them cool 
under these circumstances, nature has provided a self- 
acting bath by means of the szveat, or perspiration. When 
the temperature of the body is raised from any cause, the 
perspiration is poured out in greater quantity, which in- 
creases as the quantity of heat increases. 

The heat of the body is used in changing the water of the perspira- 
tion to steam, which then passes off from the body. The process is 



236 APPLIED PHYSIOLOGY 

like the boiling of water in a teakettle, where the heat passes off in the 
steam, so that the temperature of the water does not rise beyond the 
boiling point. Some perspiration is given off even if the body is cold, 
but with an overproduction of heat more perspiration is often pro- 
duced than can be turned into vapor. A person is usually said to per- 
spire only when it is produced in so great a quantity that it collects in 
drops upon the skin. 

414. Moisture in the air. — When there is a great amount of 
moisture in the air on a hot summer's day, the perspiration does not 
evaporate from the skin, and so heat is retained within the body, and 
the air seems " heavy" and oppressive. On such days the Juunidity of 
the air is said to be great. Dry air at a temperature of 90 or 95 degrees 
seems cooler than moist, humid air at a temperature of 80. 

415. Sunstroke. — Men and animals, while working, pro- 
duce a large amount of heat. On'excessively hot and humid 
days the extra heat may not pass off so fast as it is formed, 
but may accumulate until the temperature rises several 
degrees. The increased heat overwhelms the body, and 
produces a sudden attack of faintness called sunstroke. 
The unconsciousness lasts for a long time, and is followed 
by great weakness, and sometimes by death. When a 
person is sunstruck he should be laid in a cool place, with 
his head lowest. Cold water should be dashed upon his 
head and chest. His limbs should be rubbed to help the 
circulation. 

416. Damp days in winter. — While moisture in the air makes 
the body warmer in summer, in the winter it makes the air seem colder. 
Dry air is a poor conductor of heat, but a little moisture makes it a 
much better conductor. So a damp wind rapidly extracts the heat 
from the body, and seems to penetrate even thick clothing. Moist air 
at a temperature of 20 degrees seems colder than dry air at zero. 

417. Heating living rooms. — In addition to the means 
provided b)^ nature, man is often compelled to add devices 
of his own for regulating the heat of his body. Man lives 



HEAT AND CLOTHING 23^ 

with the greatest comfort while the temperature of the 
air is about 70 degrees, which is but Httle more than half- 
way between the temperature of freezing and the heat of 
the blood. A temperature of 80 degrees feels too warm, 
while 90 degrees is hot, and 98 1, or the temperature of the 
body, is oppressive. 

In winter a temperature of 70 degrees in a living room 
feels neither warm nor cold, and the change between it 
and the outside cold air is less noticeable than at any other 
temperature. A temperature of 75 or 80 degrees feels too 
warm, and when the person goes out of doors the cold air 
produces a sudden contraction of the arteries and a chill, 
which often results in taking cold. A sleeping room should 
be at a lower temperature than a living room. 

418. Clothing. — Man protects his body against the loss 
of heat by covering it with clothes. Some kinds of sub- 
stances readily permit heat to pass through them, and are 
called good heat conductoi's, while others carry heat poorly 
and are caWtd />oor conductor's. Lineri is a. good conductor 
of heat. It is a poor protection against cold, for it lets 
out the heat of the body, but it makes good summer cloth- 
ing. When the linen clothing is adjusted to one tempera- 
ture, a change to cooler air is quickly and suddenly felt. 
Thus it is an undesirable clothing material in changeable 
climates or in cold weather. 

Cotton, while being a poorer conductor of heat than 
linen, is yet too good a conductor to protect the body in 
cold or changing w^eather, unless a great deal is worn. 

Wool is a poor conductor of heat. When the tempera- 
ture is suddenly lowered, it permits the heat of the body 
to pass off but slowly, and thus gives the skin time to ad- 
just itself to the change. In summer it retains too much 
heat, and does not make so good summer clothing as cot- 



238 APPLIED PHYSIOLOGY 

ton or linen, but when the temperature of the air is higher 
than that of the body, it prevents the heat from entering, 
and thus is cooler than linen or cotton. So men who tend 
hot furnaces are cooler if they wear thick flannel than if 
they wear linen or cotton. 

Silk is also a poor conductor of heat. While more ex- 
pensive than wool, it is lighter in weight and feels softer 
to the skin, and so makes the best kind of clothing. 

Fur is the poorest conductor of all, and is the best pro- 
tector against cold. Nature has given a thick coat of fur. 
to animals that live in cold regions. In winter their fur 
is long and thick, but it drops out during spring, and a 
new fur grows during the summer, becoming thick and 
long again by the following winter. 

Air itself is a poor conductor of heat, and when a considerable quan- 
tity is imprisoned in the meshes of cloth, the garment offers a greater 
resistance to the passage of heat. So loosely woven cloth is much 
warmer than cloth made up of tightly twisted thread. Fur is warm 
largely because of tl^e amount of air which it imprisons. For the same 
reason loose clothing is warmer than tight-fitting clothes. 

419. Color and hea.t. — When exposed to the sun, black objects 
take up twice as much heat as white objects. This difference of tem- 
perature is noticeable in clothing. Light-colored or white clothing is 
best for summer, and dark-colored or black for winter. 

420. Distribution of clothing. — The different parts of the 
body vary in their ability to resist cold. The face and hands usually 
need no covering. The feet need less than the body, while the back, 
chest, and abdomen need the most. Nature has distributed fur upon 
the animaPs body in the same way, leaving the head and feet poorly 
covered. The sense of warmth is the best guide as to the amount of 
clothing to be worn on any part. A person should wear enough to 
keep each part of the body comfortably warm, while no part, especially 
one which is usually left uncovered, should be covered so as to be 
uncomfortably warni. 

Dampness produces cold by the evaporation of water. If all the 



1 



HEAT AND CLOTHING 239 

clothing is wet. heat is taken from the whole body equally, and there is 
equal contraction of the arteries with no congestion or inflammation. 
But if a single part is wet, it feels cold, while the rest of the body is 
warm ; so wet feet often produce inflammation of difterent parts of 
the body. 

Cold feet. — When the feet perspire a great deal, the stockings 
and soles of the shoes become saturated with moisture and make the 
feet feel as cold as if they were wet. Thicker stockings make the 
feet perspire still more, and so do not add to their warmth. Tight 
shoes allow of no ventilation, and so the moisture is retained, and the 
feet are wet and cold. 

Drying the shoes and stockings every night before the fire will pre- 
vent their becoming saturated with moisture. A new inside sole cut 
out of thick paper put in the shoe each morning will absorb moisture 
and help keep the feet warm. Rubber boots and shoes do not permit 
the moisture of insensible perspiration to pass off", and so they seem- 
ingly cause the feet to perspire. 

Bathing the feet each morning in cold water and drying them by 
brisk rubbing improves the circulation, so that they will be more likely 
to stay warm all day. 

421. Paper as a protection against cold. — Paper is a poor 

conductor of heat. A newspaper wrapped around the body under the 
coat is as good as an overcoat for warmth. A few newspapers spread 
between the quilts of a bed will make up for a lack of bed clothing upon 
a cold night. One need not suffer from insufficient clothing, day or 
night, if a few newspapers are at hand. 

422. Sufficient clothing. — The amount of clothing which 
one needs depends largely upon a person's occupation and 
previous habits. A day laborer seldom needs an overcoat, 
but works in his shirt sleeves, while a clerk would be 
chilled were he to step outdoors without extra wraps. It 
is a mistake to think that by exposure to the cold one 
can always become hardened to it. It is true only when a 
person takes active exercise and lives out of doors continu- 
ousl}\ The body cannot adapt itself to the sudden changes 
from hours spent in a warm room to an hour or two in the 
cold air. Enough clothing should be worn so that the body 



240 APPLIED PHYSIOLOGY 

does not feel chilled on entering the cold air. When by 
exercise the body feels warm, the overcoat may be unbut- 
toned or removed, but while resting it should be put on at 
once. Children often get cold by suddenly cooling off 
while warm, fearing ridicule if they should put on their 
coats_ during a few moments' rest from play. 

423. Airing clothes at night. — At night it is usually best to 
remove all clothing worn during the day. Woolens have the power of 
absorbing a great deal of moisture without feeling damp. But the 
moisture and the waste matters from the skin should be removed each 
night by thoroughly airing the underclothes. If it is not done, the 
woolen may become so saturated with moisture that it affords no more 
protection than cotton, and so may render a person liable to take cold. 

424. Beds. — Feather beds and thick quilts enable a 
person to get warm when he goes to bed on a cold night, 
but after he falls asleep he becomes too warm and per- 
spires too freely. Then he throws off the coverings, and 
soon the evaporation of the perspiration makes him cold. 
The changes from one extreme to the other often produce 
colds. Feather beds warm the side of the body which is 
buried in them, while the other side is cold. This unequal 
distribution of heat is the common cause of catching cold. 
As a rule a plain mattress is more comfortable and gives 
a more even heat than a feather bed ; but in beds, as in 
clothing, a person's sensation forms the best guide as to 
the kind to be used. 

425. Effect of lowering the temperature of the body. — 
In extremely cold weather heat may be lost from the body 
faster than it can be produced, and thus the temperature 
falls. Then the body and mind cannot act, but become 
numb and sluggish, just as the hands become numb and 
powerless when cold. If the temperature continues to fall, 
the respiration becomes less, and as the cells cease to act 



HEAT AND CLOTHING 24I 

an agreeable feeling of drowsiness steals over the mind, 
until the actions of life cease. After the drowsy feelings 
begin, life can be restored only by applying heat to the 
body and performing artificial respiration so as to start the 
process of oxidation again. 

426. Frost bites. When a part becomes very cold the 
cells may be seriously injured long before they are frozen. 
A toe or an ear which has been on the vers^e of freezinsf 
will begin to prick and tingle when warmed. For a long 
time afterward, sensations varying from an itching to severe 
pricking and smarting will cause great annoyance. In 
severe forms, short of actual freezing, the part swells and 
becomes red and inflamed, while the sensations are ex- 
tremely annoying. A part which is actually frozen is 
likely to die. The part turns black soon after being 
thawed, and has no feehng. After a few days the dead 
part comes off, leaving a raw sore. Fingers, toes, and 
ears are very liable to become frozen, but the eyelids are 
almost the last thing to freeze. 

427. Frozen limbs. — When a solution of a substance in water 
freezes, the first ice formed is composed of crystals of pure water, while 
that frozen last contains most of the dissolved substance imprisoned in 
the meshes of the crystals. The cells of the body are made of water 
in which albumin and mineral substances are dissolved. When freez- 
ing occurs, the first ice is composed of needles of pure water which has 
been taken from the cells. If the freezing takes place rapidly, the 
water produces swift currents which break down the delicate framework 
of the cells and cause their death. If freezing occurs very slowly, the 
water may leave the cells so slowly that no damage is done by the tiny 
flood. If thawing occurs just as slowly, the water may reenter the 
cells so that they may be preserved alive. When a hand or a foot is 
frozen, it should be rubbed gently either with snow or else while im- 
mersed in ice water, and the raising of the temperature of the water 
should be done very slowly, taking, at least, two or three hours for the 
thawing process. The preservation of the frozen part depends upon 

OV. PHYSIOL. — 16 . 



242 APPLIED PHYSIOLOGY 

its very slow thawing. Never apply warmth of any kind to a frozen 
part, and avoid sitting near a warm stove afterwards. 

428. Effects of raising the temperature of the body. — 

When a living body is exposed to a higher temperature 
than is natural, the respiration and circulation are much 
increased by the extra heat and there is much mental 
excitement. In fevers there are usually excitement and 
delirium. A continuous temperature of 105 degrees is 
usually fatal. 

It is possible to work in an atmosphere which has a temperature 
of 150 degrees or more, and men have remained in hot ovens for many 
minutes without harm. Their perspiration flows very freely, and its 
evaporation carries off the extra heat, so that the temperature of the 
body does not rise. If the perspiration should cease, the temperature 
of the body would rise at once, and death would soon take place. 

429. Burns. — A temperature of no degrees feels very warm, 115 
degrees is hot, while 120 degrees is all that a person can commonly 
stand. A temperature higher than this injures the cells so that a blister 
will be raised in a few minutes. A temperature of 170 degrees coagu- 
lates albumin at once and so destroys the life of cells which it touches. 
A temperature of 212 degrees, or boiling point, at once produces a deep 
scald, while higher temperatures burn the skin to a crisp. 

Cold water applied at once to a burn prevents its extension and 
soothes the smarting, but it should be applied only for a short time 
lest it should injure the cells. Common baking soda is one of the 
most soothing applications. A mixture of linseed oil and lime water 
is a good application for continuous use. After a deep burn has healed, 
a puckered scar will be left, but the scar will be less noticeable if healing 
is hastened by skin grafting. 

430. Burning clothing. — When the clothing on a person takes 
fire, a great danger is that the flames may be inhaled. It will take 
some time for the flames to penetrate to the flesh, but they may quickly 
spread upward. So a person should always lie down at once. Then 
let him roll over and over so as to crush out the fire. Even if the fire 
is not extinguished, the flames cannot reach the face, while the clothes 
can be removed as well lying down as while standing. In helping a 



HEAT AND CLOTHING 243 

person whose clothes are burning, at once throw the person to the floor. 
Many have lost their lives by persisting in standing up while attempt- 
ing to remove the burning clothes. 

If it is necessary to enter a burning building, or to carry a person 
whose clothes are burning, the best protection will be to wrap a thick 
coat or blanket around the body. A thick coat wrapped around burning 
clothes or thrown over the body after a person lies down will quickly 
smother the flames. 

431. Alcohol and heat. — The amount of heat in the 

body depends upon the balance between its production 
and its loss. The rapid destruction of alcohol, in all 
probability, yields heat too rapidly to be utilized by the 
body. The most constant effect of taking alcohol is to 
dilate the arteries of the skin, so that an extra amount of 
heat is lost. More heat is always lost than is produced. 
Alcohol lessens the power of the body to endure cold. On 
a cold day when the arteries of the skin are contracted so 
that there is but little blood to w-arm its nerves, alcohol 
may send the blood to these nerves and produce an agree- 
able sense of warmth, but in reality this feeling of warmth 
is due only to the heat which is passing off from the inte- 
rior of the body. 

432. Regulation of temperature in the dog. — The temper- 
ature of many animals is slightly above man's temperature, 
but is regulated in the same way. Some, like dogs, sweat but 
little, but the animal takes short and rapid breaths through 
his open mouth, thus creating a strong current of air over its 
moist surface. The evaporation of the saliva cools the blood. 

433. Hibernation of animals. — When winter comes on, 
some animals, like the woodchuck, retire into their holes 
and go to sleep. Their temperature falls to 50 degrees, 
or even lower, while respiration occurs only three or four 
times a minute. Only enough oxidation of their own 
bodies occurs to keep life from completely dying out. 



244 APPLIED PHYSIOLOGY 

When warm weather comes again, their respiration and 
temperature rise to the natural point, and the animal re- 
sumes its former condition, but is thin from the oxidation 
of its fat and albumin during his long sleep. The dormant 
state during the winter is called hibernation. 

434. Cold-blooded animals. — In frogs and snakes, oxi- 
dation is not sufficient to raise their temperatures much 
above that of the surrounding air. So they feel cold to 
the touch, and are called cold-blooded. On warm days 
they do not lose heat so rapidly, and more heat is retained 
within their bodies, and thus they become more active. 
When cold weather comes on, they cannot produce enough 
heat to enable them to move, but they lie unconscious 
until warm weather comes again. 

Insects cannot produce enough heat during winter to 
enable them to fly about, so they remain apparently life- 
less until the warm weather comes again. 



SUMMARY 

The heat developed by oxidation is distributed through 

the body by the blood so that everywhere it has a 

temperature of 98.5 degrees. 
The sensations of heat and cold are caused by the 

blood circulating in the skin. If little circulates, 

we feel cold; while if much circulates, we feel 

warm. 
An increased quantity of food, oxygen, or exercise 

increases the amount of heat produced in the body. 
Heat is given off by contact of the skin with the cold 

air and by means of the perspiration. 
A temperature of about 70 degrees in a room is the 

most comfortable. 



HEAT AND CLOTHING 245 

6. Moisture in the air prevents the evaporation of per- 

spiration, and increases the feehng of warmth. 

7. Fur, silk, woolen, cotton, and linen protect the body 

from cold in the order given. 

8. Raising the temperature of the body causes excite- 

ment and delirium. 

9. Alcohol dilates the arteries of the skin and permits 

an increased loss of heat, in spite of the feeUng of 
warmth. 
10. In animals while hibernating, and in all cold-blooded 
animals, oxidation is feeble, the temperature is low, 
and their movements are sluggish. 

DEMONSTRATIONS 

97. To show that more blood goes to a part, and that it becomes 
warmer while acting, let a boy roll up his sleeve and hang his arm by 
his side. Notice that the veins slowly fill, because the flow of blood is 
slowed by running up hill. Now have him open and shut his hand 
rapidly, and notice that at once the veins become filled full of blood. 
After a moment the hand feels warmer than the other, especially if 
they were a little cold at first. 

98. Take some ice water, some water at the temperature of the air, 
and some hot water. Notice that the water at the medium temperature 
feels warm when the hands have just been taken from the ice water, 
but cold when they have just been in the hot water. 

99. Feel of a piece of iron and of a stone after exposing both to the 
cool outside air. Notice that the iron feels colder, for it takes heat 
from the hand faster. 

100. To show that obstmcting the flow of blood makes a part 
cold, tie a string rather tightly around the finger. In a moment it 
becomes filled with venous blood, and feels cold, for the blood is 
not renewed. 

loi. That the sensation of heat and cold depends partly upon the 
amount of blood in the skin can be shown by holding a piece of ice in 
the hands for several minutes. At first, the hands feel cold, for the 
arteries are contracted. In a little while the blood circulates freely 



246 APPLIED PHYSIOLOGY 

again, and there is a feeling of warmth, although the ice still continues 
to cool the hand. 

102. Take some cotton and some woolen cloth of equal thickness. 
Wet them and notice how much more quickly the cotton will dry than 
the wool. Wrap them around the hand and notice that the woolen 
feels warmer, because evaporation from it does not carry heat away 
from it so fast as from the cotton. Then blow upon them and notice 
how much colder the cotton feels. 

103. Place two pieces of ice of equal size in the sun and cover one 
with a black cloth and the other with a white piece of the same kind, 
and notice that the piece under the black cloth melts faster. 

104. Needles of water crystals can be shown by setting aside a cup 
of water out of doors until it just begins to freeze, if it is a cold day, or, 
if it is a warm day, by putting a large piece of ice in the sun and break- 
ing it when it is half melted. Each needle is pure water. 

105. A wasp or a fly will illustrate the hibernation of animals. In 
-winter a few wasps can usually be found in a sunny garret window. 
When the air is quite warm, the wasps will be lively, and as it becomes 
colder they become more sluggish, until at night they are apparently 
lifeless. 

REVIEW TOPICS 

1. Give the temperature of the body and tell how the 

heat is distributed. 

2. State what causes sensations of heat and cold, and 

how the body may feel warm while it is cold, and 
cold while it is warm. 

3. State how the production of heat is regulated. 

4. State how the amount of blood in the skin regulates 

the amount of heat given off. 

5. State how the perspiration regulates the amount of 

heat given off. 

6. State how tight bands about a limb cause cold feet or 

hands. 

7. Give the best temperature of Hving rooms and of bed 

rooms. 



HEAT AND CLOTHING 247 

8. Give the effect which moisture in the air has upon the 

heat of the body during summer and during winter. 

9. Give the value of linen as a protection against heat 

and cold ; of cotton ; of wool ; of fur ; and of air. 

10. State how color affects temperature. 

11. State how much clothing should be worn, and how it 

should be distributed over the body. 

12. Discuss feather beds and thick bed coverings. 

13. Give the effects of lowering the temperature of the 

whole body ; of frost bites ; of frozen limbs ; and 
their treatment. 

14. Give the effects of raising the temperature of the 

body, as in fever and in sunstroke. 

15. Give the effects of alcohol upon the temperature of 

the body. 

16. State how a dog's temperature is regulated. 

17. Describe the hibernation of animals. 

18. Describe oxidation in cold-blooded animals, and in 

insects. 



CHAPTER XXVI 
EXCRETION AND SEWAGE 

435. Getting rid of oxidized and waste substances is 
excretion. All oxidations in the body produce carbonic 
acid gas and water. In addition, the oxidation of albu- 
min produces a substance called urea, which contains 
the nitrogen of the albumin. These substances together 
with the minerals or ashes left from the burned cells 
must continuously be excreted by the lungs, liver, intes- 
tine, skin, and kidneys. The kidneys excrete the most 
harmful of the waste substances. 

436. Difference between a secretion and an excretion. — 
In a general way, anything separated from the blood by 
glands is a secretion. But the term strictly is applied only 
to those substances which, like saliva and gastric juice, 
are of use to the body. Substances which, hke carbonic 
acid gas and urea, are only waste and harmful products, 
are true excretiojis. 

437. Sweat glands. — Numerous coiled tubes lined with 
epithelium project into the skin over nearly its whole sur- 
face. Each tube is a sweat gland, whose epithelium is 
continually secreting Ih^ sweat, or perspiration. They are 
very numerous on the forehead, chest, palms of the hands, 
and soles of the feet. Only a few are found in the upper 
part of the back. 

438. The perspiration. — The perspiration is over 99 per 
cent water. It contains a small amount of urea and min- 
eral substances. Ordinarily it evaporates so fast that its 

248 



EXCRETION AND SEWAGE 



249 



presence is not noticed. Nearly a quart of water a day 
thus passes off from the surface of the body in insensible 
perspiration. In hot weather and during exercise so much 
is produced that it accumulates in drops upon the skin. 

439. The kidneys. — The main work of excretion is 
performed by the kidneys. There are two kidneys, one on 
each side of the backbone, half 
covered by the two lower ribs. Each 
kidney is bean-shaped, about four 
inches in length, by two in breadth, 
and one in thickness. It is com- 
posed of millions of fine tubes made 
up of epithelial cells; they unite, and 
finally open into a pocket on the side 
of the kidney. 

440. How the kidneys excrete. — 
The epithelial cells of the tubes have 
the power to draw urea and mineral 
substances from the blood. They 
also extract a large amount of water 
in order to wash away the excreted matter. The excre- 
tion runs down a tube called the 7ireter to the bladder. 
About a quart and a half of a fluid called itrhie is thus 
excreted daily. 

441. Kidney disease. — Kidney disease usually takes the form 
of an aggravated bilious attack.. There are headaches, loss of appetite, 
coated tongue, and great weakness. Usually the urine is diminished, 
and contains some albumin derived from the blood. 

Urea itself is as harmless as carbonic acid gas and is as easily 
excreted, but when oxidation is incomplete, substances are produced 
which are as much more harmful than urea as a smoking lamp is more 
unpleasant than one burning perfectly. When more food is eaten than 
can be oxidized, poisons are developed from the imperfectly oxidized 
albumin. Some are leucomaines or substances like them. The kid- 




Kidney cut across. 



250 APPLIED PHYSIOLOGY 

neys try to excrete the poisons, but they become overworked, producing 
what is called Drighfs disease. Then the sweat glands excrete more waste 
matters, and in the emergency often do enough to relieve the kidneys. 

442. Relation of the skin and kidneys. — The skin excretes 

but little urea compared with the kidneys, yet its capacity for excreting 
water is unlimited. When much water is excreted by the sweat glands, 
only a little is excreted by the kidneys, and when little perspiration is 
formed, the kidneys excrete more v/ater. The amount of urea remains 
nearly the same from day to day, and so the urine will be more colored 
at one time than another. 

The amount of perspiration is governed principally by the tempera- 
ture, and remains nearly the same whether much or little water is taken. 
The amount of urine is increased by the water swallowed. A large 
amount of water tends to wash away the urea more perfectly. Often 
when one thinks that he has kidney trouble, an increased amount of 
water swallowed will pass through the kidneys and bring their secre- 
tion to a natural appearance. 

443. Excretion of poisons swallowed. — When poisons have 

been swallowed, those which pass by the liver are seized by the kid- 
neys and excreted. Carbolic acid and turpentine are thus excreted by 
the kidney. In passing through the kidneys these drugs may irritate 
their cells and set up inflammation. Most drugs, whether they are 
vegetable or mineral, pass out by the kidneys. 

444. Excretion by the liver. — The liver is constantly 
destroying all kinds of poisons, which it receives not only 
from the blood of the intestine, but also from the rest of 
the body. Two bile substances, glycocJiolic and taurocholic 
acids, are probably formed directly from albumin ; and 
while they are excretory products, yet they are elements 
essential to digestion. Another substance, biliiaibin, con- 
tains most of the waste coloring matter of the blood. 
When the liver fails to excrete these substances, as in 
jaundice, they pass out by the kidneys and color their 
secretion yellow. 

445. Excretion by the intestine. — Although the intes- 
tine absorbs food, yet it also pours out some waste matters. 



EXCRETION AND SEWAGE 2$ I 

When the intestme does not expel its contents, symptoms 
like liver and kidney diseases arise. So the intestine 
excretes some waste matter. Under certain conditions 
even the stomach may become an excretory organ, and 
vomiting may be a life-saving act, just as it often is when 
poisons are swallow^ed. 

446. Intemperance and kidney disease. — Alcohol, by 
disturbing oxidation and the liver, is especially liable to 
cause the production of poisons whose excretion severely 
taxes the kidneys. It alone causes over one half of kidney 
diseases. Candies, pie, cake, and preserves are all eaten 
simply for their taste, and usually after a sufficient amount 
of proper food has been taken. So, in oxidizing this 
increased amount of food, some must be imperfectly oxi- 
dized. Thus poisons are developed and the kidneys are 
overworked. 

hitemperance in sugar eating is extremely common. It 
produces imperfect oxidation in the same way as alcohol, 
only its effects are much slower and less noticeable. 

447. Sewage. — The excretions of man and animals, 
together with the dirty water used in washing, is sewage. 
Sewage is composed of substances which are of no use to 
man, but on the contrary are often very poisonous. 

448. Purification of sewage. — Nature is very efficient in 
changing sewage so that it is no longer harmful. In the upper layers 
of the soil it is fully oxidized to carbonic acid gas and water and min- 
eral substances. The soil can dispose of a great quantity of sewage and 
prevent it from polluting the surrounding wells. 

In the second place, plants feed upon sewage. They aid in its oxi- 
dation and use it as food. Thus plants may form again the substances 
which were oxidized in man's body so that he may eat the very prod- 
ucts which he once excreted. 

In the third place, running water washes away sewage, and by means 
of the oxygen which it always contains it fully oxidizes the excretions. 



252 



APPLIED PHYSIOLOGY 



449. Danger from sewage. — Sewage often is a poison 
itself, and when much is collected it often develops poisons 
by its decay. The foul smell of sewage is due to gas 

called sewer gas. While 
the gas itself is but slightly 
harmful, yet it is a sign 
of decay and of lurking 
sources of danger. Sew- 
age is dangerous, niainly 
because it may furnish 
food in which germs of 
disease may grow. Ty- 
phoid fever is often trans- 
mitted in this way. These 
germs may become dry 
wherever the sewage dries, 
and may then rise as dust 
with the sewer gas. 

450. Disposal of sewage. 
— In thinly settled country 
places nature is able to dis- 
pose of the sewage so that 




Diagram of the plumbing of a house. 

a sink or washstand. 

b trap, which remains full of water and pre- 
vents the entrance of sewer gas. 
c air pipe for ventilation and to prevent the '^^ jg dcstrovcd whcrCVCr it 



water from being sucked out of the 
trap. 



is placed. But in order to be 

d waste pipe, down which the slops pass g^^.^ ^^ ^^^-^ pollution, the 

into the sewer. ^ 

e pipe from the gutter on the roof. 
/ waste pipe passing under the street. 
g ventilation pipe. 



simplest contrivance is to 
conduct the sewage away 
from the house and into a 
hole, from which it slowly filters through the ground. 

In more thickly settled places the hole in the ground 
is often made water-tight, forming a cesspool. 

451. Sewers. — Towns and cities provide large under- 
ground tubes or tunnels, called sewers, into which the 



EXCRETION AND SEWAGE 253 

sewage runs from each house. The sewage is either 
emptied into running water and is carried away by the 
current, or else it is transported to a distance from the 
city and spread over the soil of a farm, where it becomes 
plant food. The produce raised upon the farms aids in 
paying the expense of removing the sewage. 

452. Plumbing. — In houses pipes are arranged to carry 
off the sewage as fast as it is formed in the sinks, wash- 
bowls, and closets. Since they open into a common 
sewer of the town, sewer gas can readily enter the 
houses. To keep it out, each pipe is bent into a loop 
which remains full of liquid and prevents the entrance 
of gas. 

453. Cleanliness. — No matter how good the natural or artificial 
drainage may be, if decaying matter is left in cellars it may poison the 
air. Sinks may become clogged and poison the air, while slops and 
dirty dishes may be carriers of disease. So cleanliness is of great im- 
portance, aside from its mere looks. 

454. Choice of a house. — Damp soils are likely to breed dis- 
ease. In some the subsoil is clay or solid rock and does not permit 
the sewage to pass off. Land formed by filling in marshes is apt to be 
damp and malarious, besides affording no natural drainage. 

The site for the home should also be such that the barnyard and 
outhouses can be put so they will drain away from the house and well. 
Attention to these details of drainage is of far more importance than 
the natural beauty of a site. 

SUMMARY 

1. Excretions are waste and poisonous substances ex- 

pelled from the body. The principal ones are car- 
bonic acid gas, water, urea, and mineral matters. 

2. Sweat, or perspiration, is formed in tubes in the skin. 

It excretes some urea and mineral matters. 

3. The kidneys are collections of minute tubes which sepa- 

rate urea, mineral matter, and water from the blood. 



2 54 APPLIED PHYSIOLOGY 

4. When, in Bright's disease, or from any other cause, 

the kidneys cease acting, death by poisoning soon 
takes place. 

5. The skin can aid the kidneys, but cannot take their 

place. 

6. Alcohol causes poisons to develop whose excretion 

overworks the kidneys. 

7. The liver and intestine each excrete a great amount 

of waste and poisonous substances. 

8. The excretions from man remain poisonous until 

destroyed by the soil, by plants, or by running 
water. 

9. In thickly settled districts it is necessary to carry off 

the excretions by means of a sewer. 



DEMONSTRATIONS 

106. Carefully weigh several boys early on a warm day. Have 
them run about and take violent exercise, eating and drinking nothing, 
or only known amounts. In a few hours weigh them again. A loss of 
half a pound or more may be noted. 

107. Insensible perspiration may be shown by touching a cold glass 
to the skin, when moisture will at once condense upon the glass. 

108. Secure a specimen of kidney mounted for the microscope. 
With a power of about 200 diameters show the class how capillaries 
form a bunch in a pocket at the beginning of each tube, and then pass 
out to surround the tubes, and finally unite to form the veins. Show 
them the large size of the cells of the tube. 

109. Cut open a pig's or sheep's kidney lengthwise and notice the 
pocket in its side and the radiating lines of the kidney reaching almost 
to the surface and marking the course of the tubes. 

1 10. A pot of growing flowers will illustrate nature's method of dis- 
posing of sewage. Although manure and dirty water are poured upon 
the earth, yet they give out no odor, but become fresh and clean and 
nourish the plant. 

111. Show the pupils the traps for sewer gas under the sinks. 



EXCRETION AND SEWAGE 255 

REVIEW TOPICS 

1. Explain the difference between a secretion and an 

excretion. 

2. Name the principal excretions and tell how they leave 

the body. 

3. Describe sweat glands and the perspiration as an 

excretion. 

4. Describe the kidneys and their excretion. 

5. Discuss how imperfect oxidation may overwork the 

kidneys. 

6. Show how the skin aids the action of the kidneys and 

how the one acts less when the other is more active. 

7. Show how alcohol prodiices kidney diseases and how 

sugar acts in the same way. 

8. Describe three ways in which nature destroys the 

excretions of man. 

9. Discuss the dangers which may arise from sewage. 

10. Tell how sewage is disposed of in cities. 

11. Describe how sewer gas is prevented from entering 

houses through waste pipes. 



CHAPTER XXVII 



THE SKIN AND BATHING 



455. The derma. — The skin is the tough, loose sack 
which covers the entire body. It is designed to protect 

the body and to give 
off perspiration and 
heat. (See pp. 235, 248.) 
The main part of the 
skin is a tough, elastic 
network of fibers, called 
the derma or ciitis^ which 
forms a layer from -^^ to 
\ of an inch in thickness. 
The derma of animals, 
when tanned, forms 
leather. The skin is 
connected with the body 
by a loose network of 
-fibers called the subcu- 
taneous tissue, which per- 
mits the skin to move 
freely over the deeper 
parts. Over some parts 
of the body, as upon the 
abdomen, the subcutane- 
ous tissue contains a 
thick layer of fat. 




The skin (x 100). 

a dead layer of epidermis. 

b growing layer of epidermis. 

c layer of cells containing the coloring 

matter of the skin. 

d papilla. 

e sweat gland. 

f small blood tube. 

g fibers of the derma. 

h fat cells in the derma. 



256 



THE SKIN AND BATHING 



257 



456. The epidermis. — The derma is covered with a layer 
of epithelial cells, called the epider7nis or cuticle. New 
cells are continually being produced in the deeper layers 
of the epidermis, while the older cells become matted in a 
firm mass which is continually being worn away. These 
cells are directly continuous with the epitheUal cells of the 
mucous membrane and are of the same nature. The epi- 
dermis has no nerves and no blood tubes. 




A com. 

457. Upon the palms of the hands and soles of the feet the epi- 
dermis forms a very thick layer for the better protection of these much- 
used parts. When hard labor is performed with the hands, nature 
causes the protecting epidermis in the exposed parts to form a thick 
and horny spot called a callus. Sometimes pressure and rubbing cause 
a small area to become thickened so that a point of hardened cells is 
formed which presses into the deeper parts of the skin. This is a com. 

When the skin is vigorously rubbed, or certain drugs are applied, 
the deeper layers of the epidermis are killed, and water accumulating 
between them and the outer layers raises a blister. 

458. Color of the skin, — The deeper layers of the epidermis 
contain colored granules which give the peculiar color to different races 
of men. Exposure to the sun's rays produces a darker coloring matter. 
In some people the coloring matter is deposited in small spots called 
free tiles. 

ov. PHYSIOL. — 17 



258 



APPLIED PHYSIOLOGY 



459. Skin grafting. — A spot of skin deprived of epithe- 
lium is tender and sore. New flesh forms over its surface, 
while the epithelial cells at its edge produce new ones 
which spread over the whole surface and complete the 
healing. If they do not grow, the new flesh sprouts above 

the skin, forming 

^^^'^^f ...^^^-^ P^'o^^^ flesh. 

The deeper cells 

of the epidermis 

may remain alive 

for some hours 

after being cut off 

from the body. 

^ When placed upon 

a clean ulcer, they 

^may grow and 

r produce a new epi- 

g thelium. This is 

ski7i grafti7ig. 

460. Papillae. 
— From the sur- 
face of the derma 
small projections 
about 2^Jq^ of an 
inch in length, 
called papillcE, ex- 
tend a short dis- 
tance into the epidermis. They contain nerves of feeling. 
The papillae over a small area sometimes become over- 
grown, so that they project above the skin, forming a 
wart. Rows of papillae form the fine curved lines upon 
the balls of the fingers and the palms of the hands. They 
are most numerous where the sensation of touch is greatest. 




"if' 



A hair (x 200). 

a epidermis of the skin. 

d hair shaft. 

c sebaceous gland. 

d muscle which makes the hair erect. 

e epidermis of the hair root. 

/ fat cells in the derma. 

^ papilla from which the hair grows. 



THE SKIN AND BATHING 259 

461. Hair. — Extending obliquely nearly through the 
derma are numerous minute tubes lined with epithelium. 
Their cells .become joined together in a tough string, called 
a Jiair, which projects out of the tube. When the hair is 
pulled out, the epithelium covering the projection in the 
tube soon produces another hair. A small muscle is 
attached to the bottom of each hair root. Cold causes 
the muscles to contract and to pull the hair tubes to an 
upright position imparting to the skin a roughness called 
goose flcsJi. Hair covers almost the entire body. 

462. Sebaceous glands. — Near each hair is a gland called 
a sebaceous gland. It secretes a kind of oil, which softens 
the skin and keeps the hair glossy. The glands are espe- 
cially numerous down the center of the face. When their 
mouths are stopped by 
dirt they often become 
distended and form small, 
black spots called black- 
heads, which are often 
mistaken for small worms. 

463. Nails. —The epi- 
dermis upon the backs of 
the last joint of each finger 

and toe is hardened into a * •, . ^ 

A nail ( X 200) . 

nail. The nail is formed ^ surface of the nail, 
at its back part and is b body of the nail. 

, , , . .^ c epithelial cells just before they are welded 

pushed onward m its into a nail. 

growth. An epithelial cell ^ papillae. 

remains a part of the nail 

about three months before it is pushed from its root to its 

end. 

464. The complexion. — In liealth the skin lias a velvety appear- 
ance, and a rosy color, and is free from spots or scales. Its moisture is 




e growing epithelium. 



26o APPLIED PHYSIOLOGY 

of the proper degree to cause it to feel soft and pliable. Its appearance 
is changed by ill health. If the stomach and intestine are not in good 
order, it is almost impossible for the skin to be beautiful. Plain food, 
fresh air, and exercise make a beautiful skin, and no skin can be beauti- 
ful without them. Cold dry air or exposure to the sun's rays often 
cause it to become red or to blister. These effects are much greater 
upon those who are unaccustomed to the exposure. 

465. Care of the complexion. — Washing the skin with soft 
water and soap as often as it becomes dirty, and following it by a 
thorough drying with a soft towel, are the only effective means of 
beautifying the skin. Paint, powder, and perfumery cannot cause the 
skin to grow more beautiful. They simply coat its outside, and at the 
same time stop' its sebaceous and sweat glands, so that when, it is 
removed the skin looks worse than before. They act like any other 
dirt. Many of these preparations contain poisonous minerals such as 
lead. 

Drugs taken internally to beautify the skin act mainly through the 
arsenic which they contain. Arsenic destroys the blood cells, and so 
gives a peculiar paleness to the skin. Paleness is only a sign of poison- 
ing which is working harm to the health. 

466. Absorbent power of the skin. — Since the outer part 
of the epidermis is dry and dead and contains no blood 
tubes or lymphatics, substances rubbed upon the skin 
will not be absorbed. So man can handle virulent poisons 
and disease germs without danger. On the other hand, 
when the epithelium is removed, the exposed blood tubes 
and lymphatics take up drugs and poisons very readily. 
Drugs may be absorbed from surgical dressings, and germs 
of disease may enter through even a minute scratch. 

467. Care of the hair. — The hair of man, like that of animals, 
is soft and glossy in health, but often dry and rough during disease. 
Daily brushing to remove the dirt, and to distribute the oily secretion 
of the sebaceous glands, will keep the hair in the best condition. All 
that is necessary beyond this is frequent washing with soft water. The 
secretion of the sebaceous glands is sufficient to oil the hair and s-calp. 
There is no substance which will cause hair to grow, neither will any 



THE SKIN AND BATHING 261 

stop its growth. When hair is shaved off, it soon regains its former 
length and then ceases to grow. Shaving seems to have some effect 
in causing the hair to grow coarser, but it does not add to the number 
of separate hairs. 

468. The beard. — At about the age of sixteen the hair upon a 
boy's face begins to grow larger and coarser, and if let alone becomes 
a full beard in the course of two or three years. A shaved beard is not 
so silky as one that has never been cut. 

A beard gives to a young man an appearance of age and experience 
and is popularly taken for a sign of mental and physical strength. As 
a matter of fact the presence or absence of a beard has nothing to do 
with a person's experience or knowledge. 

469. Care of the nails. — Biting the nails makes their edges 
ragged, besides making the ends of the fingers sore. The nails them- 
selves are not poisonous, but underneath their projecting ends germs 
of disease may be mixed with the dirt which gathers there. Naturally 
the nail adheres to the finger nearly down to its end, but is often kept 
raised and sore by too persistent cleaning. The edge of the semicircle 
of flesh surrounding the root of the nail is naturally soft and slightly 
raised so that it looks like a fine silken braid. Sometimes it becomes 
hard and cracks, especially upon cold, dry days. Cutting away the 
hard edge down to its soft margin in the flesh prevents the extension 
of the cracks. A tiny sliver of the edge of flesh around the nail torn 
back into the flesh forms a hangnail. The hangnail should be cut off 
close to the flesh. It is best prevented by gently pushing the skin 
back from the nail. Tight shoes bind the toes together, curving the 
great toe nail into the flesh, causing an ingrowing toe nail. Broad 
shoes are the best preventive of the trouble. 

470. Bathing. — A noticeable odor of perspiration about 
any part of the body is a sign of imcleanliness, and is the 
best indication of the need of a bath. Even in cold weather 
a bath is needed at least once a week, while in the summer 
it may be necessary to bathe daily. Soap and hot water 
soften the epithelium, and if the skin is then rubbed vigor- 
ously, a large amount may be rolled into small balls, which 
are often supposed to be dirt. When much epithelium is 
removed in this way, the body is more sensitive to the cold, 



262 APPLIED PHYSIOLOGY 

the perspiration passes off with greater ease, and the skin 
is made tender. 

471. Hot baths. — The heat of a bath in which the body- 
is kept warm from the time it enters the water until it is 
dry dilates the blood tubes of the skin, so that the blood 
accumulates upon the surface. Thus the internal organs 
contain less than their natural supply of blood, and the 
body is apt to feel weak and drowsy. After mental labor 
a hot bath may cause the blood to leave the brain and so 
bring about sleep. When a cold is coming on, a hot bath 
may attract blood away from the throat and bronchi so 
that the inflammation is cut short. The proper time for 
a hot bath is at night, just before retiring, so that the cir- 
culation may become natural before morning. A hot 
bath requires the use of a warm room, and of a tub suffi- 
ciently large to admit most of the body at once, for evap- 
oration of the warm water causes a cold feeling on coming 
out of the bath. It should always be followed by rest or 
sleep. 

472. Cold baths. — When a cold bath is taken, the blood 
tubes of the skin at first contract and give a cold feeling ; 
but they soon dilate. With the dilatation there comes an in- 
creased flow of blood throughout the whole body, so that 
there is a feeling of warmth and vigor in marked contrast 
with the drowsiness of the hot bath. The invigorating 
effects of a bath are called its reaction. If a cold bath 
is long continued, there comes on a second contraction of 
the arteries, so that the blood Ms forced within the body, 
producing a feeling of coldness and weakness from which 
the body is a long time in recovering. This second con- 
traction of the blood vessels is called the secondary reaction. 
The bath should be stopped at the first appearance of a 
chill. 



THE SKIN AND BATHING 263 

473. An easy way of bathing. — A cold bath requires nothing 
more than some water and a towel. A simple wetting of the body with 
the hands, followed by rubbing with a soft towel, produces all the effects 
of an elaborate bath tub. Such a bath can be taken in two minutes 
upon rising and is very invigorating and refreshing. 

474. Turkish baths. — A Turkish bath is a combination of hot 
and cold baths in which the body at first is made to perspire in a hot 
bath while being rubbed. The body is then suddenly deluged with 
cold water and rubbed dry. At night the bath is refreshing, but the 
removal of epithelium and the excessive perspiration make the bather 
liable to take cold. 

475. Sea bathing. — Running water carries off the heat of the 
body, and thus produces a greater effect than still water. The motion 
of the waves makes sea bathing exhilarating, and the salt in the water 
seems to have some stimulating effect. 

476. Bathing in fevers. — A cold bath always lowers the tem- 
perature of a feverish person, and if properly given, greatly adds to his 
comfort. It also stimulates the skin to greater activity so that it aids 
the kidneys in their work of excretion. A good way of bathing a 
feverish person is to uncover only an arm, and wet it wath lukewarm 
water. Then gently rub it with the bare hands until it is dry. The 
evaporation rapidly produces an agreeable coldness, while the rub- 
bing keeps up the circulation and prevents taking cold. Then cover 
it and go over the other arm, and then the legs, and the body in 
the same way. Finish by washing the face and brushing the teeth. 
It is proper to give such baths several times a day if the fever is 
high. 



SUMMARY 

1. The skin consists of a thick network of connective 

tissue, called the denna, covered with several layers 
of epithelium, called the epidermis. 

2. A hair is formed by the welding together of epithelium 

in a minute tube in the skin. 

3. Sebaceous glands pour an oily substance upon the hair 

roots to soften the skin and hair. 



264 APPLIED PHYSIOLOGY 

4. At the backs of the ends of the fingers and toes the 

epithelium is thickened and hardened to form the 
nails. 

5. Digestive disturbances are the principal causes of a 

poor complexion. 

6. Paints and powders irritate the skin and have the 

same effect as dirt. 

7. Daily brushing the hair and frequently washing it 

with soap and water are the best means of keep- 
ing it soft and glossy. 

8. Nails should be smoothly trimmed, and gently cleaned. 

9. The skin should be washed often enough to prevent 

an odor of perspiration. 

10. The heat of hot baths dilates the arteries of the skin 

so that blood leaves the internal organs and brain 
and produces a feeling of rest and drowsiness. 

11. A cold bath contracts the arteries of the skin. But 

they soon dilate and produce a feeling of warmth 
and exhilaration, called the reaction. 

12. If a cold bath is continued, the arteries again contract, 

producing chilliness and a feeling of exhaustion. 

DEMONSTRATIONS 

112. Examine a specimen of skin with a microscope. Notice the 
network of connective tissue in the derma, and the numerous arteries 
and veins. Notice its projections of papillae and their covering of 
epithelium. Notice that the epithelial cells in the deepest layers are 
large and round, and the outermost layers are flat and shriveled and'can 
scarcely be.recognized. Notice a. faint line of colored granules in the 
third or fourth layer of cells. In a negro the colored layer is very dis- 
tinct. The specimen will also probably show one or two winding sweat 
glands. 

113. The skin specimen will probably show a few hairs, but one 
specially prepared will be better. Notice the deep tubelike depression 



THE SKIN AND BATHING 265 

in which the hair rests, and the Httle knob embraced by the hair at its 
bottom. Notice the whitish cells of* the sebaceous glands reaching off 
from the side toward which the hair points. Underneath the gland will 
likely be seen the faint outlines of the small muscle which causes the 
hair to stand on end. 

114. A specimen of nail under the microscope will appear almost 
transparent, but the papillae of the skin and the young epithelial cells 
beneath it will show well. 

115. Wash a boy's arm. Then apply a cloth wet in hot water for 
a few minutes and show how the softened epithelium can be rubbed 
off. Explain that it is not dirt, but the protection of the arm. 



REVIEW TOPICS 

1. Describe the skin, its derma, epidermis, subcutaneous 

tissue, and coloring matter. 

2. Describe the modifications of epidermis in a callous 

spot and a corn. 

3. Describe freckles ; a blister ; an ulcer. 

4. Describe the papillae. 

5. Describe a hair, sebaceous glands, and blackheads. 

6. Describe the nails. 

7. Give the causes and treatment of a bad complexion, 

and the effects of paints and powders and drugs. 

8. Give simple directions for the care of the hair. 

9. Give simple directions for the care of the nails. 

10. Give a general rule when to bathe for cleanliness. 

1 1. State the effects of a hot bath, and when to take it. 

12. State the effects of a cold bath, and give a simple and 

easy way of taking one. 

13. Describe a Turkish bath, and give reasons for not soak- 

ing and rubbing the skin to an excessive degree. 

14. Give an easy way of bathing a feverish person. 



CHAPTER XXVIII 
NERVES 

477. Uniformity of cell action. — Certain cells forming 
the nervous system are set apart for purpose of command- 
ing the rest to work in the proper time and manner. The 
commanding cells, called nerve cells, form the essential 
part of the brain and spinal cord. From them as a center, 
fine threads called nerves run to the cells of the body. 
The outer end of each nerve thread touches a company of 
cells and carries to them the orders from the central nerve 
cells. Although each cell in the body lives and acts inde- 
pendently of the rest, yet the central nerve cells cause all 
to act in harmony. 

478. Nerves. — Each nerve thread is composed of a 
central fiber surrounded by a protective layer of a kind 

of fat. The whole 
thread is only about 
^Q^QQ inch in diam- 
eter. Those which 
go to each part of 
the body, as a hand or leg, run together in a bundle, which 
divides into its separate threads upon reaching its destined 
part. Each bundle of nerve threads is usually called a 
nerve. The main nerves of the arms are about the size 
of knitting needles, while the great sciatic nerve of the 
leg is as large as the end of the little finger. 

266 



A nerve thread (X 400). 
a central conducting fiber. b covering of fat. 



NERVES 



267 



As a general nile, a large nerve accompanies an artery do\Yn the 
inside of each limb and across the center of joints upon the side toward 
which the limb is bent. Thus they are in protected positions. One 
nerve cord is situated on the inside of the back of the elbow joint 
and is called iho. fiuniy bone. Owing to its unusual position, it is some- 
times hit, producing a pain in its ending on the inside of the hand. 




479. Nerve action. — ^When one of the main nerves of 
the arm is irritated, as by a pinch or prick, or shock of 
electricity, an impulse is started along the nerve in each 
direction. It goes to the brain 
and produces a sensation either 
of pain or j^leasure. It also 
goes to the muscle cells of the 
arm, causing them to contract 
and move the arm. If a nerve 
is cut and the end nearest the 
brain is irritated, a sensation 
will be felt, but there v/ill be 
no motion. If the other cut 
end is irritated, the muscles 
will move the arm, but no feel- 
ing whatever will be produced, 

Whether the nerve be irritated at its outer endings 
at the cells or anywhere in its course, an influence will 
travel to the central nerve cells carrying the news, and 
also in the opposite direction to the cells of the body, 
causing them to act. The cells of the body can originate 
influences which travel up the nerve to the central nerve 
cells ; and, on the other hand, the nerve cells can origi- 
nate influences which travel to the cells of the body and 
cause them to act. Transmitting impulses is the essential 
duty of nerves. They may be compared to telephone 
wires which transmit any kind of electrical influences over 



A thin slice from the end of a cut 
nerve (X 200). 

a nerve thread. 

b connective tissue binding the 
threads into a cord. 



268 APPLIED PHYSIOLOGY 

their whole length without affecting anything in their 
course. 

480. Kinds of nerves. — Each thread of a nerve trans- 
mits influences in only one direction. Some threads carry 
influences only from the cells of the body to the central 
nerve cells. Because they often produce sensation they 
are called sensory nferves. Other threads carry orders for 
action from the nerve cells to the cells of the body and 
are called motor nerves. Most nerves are made up of 
both sensory and motor threads, but some are wholly sen- 
sory and others wholly motor. There is no difference in 
their appearance. 

481. Distribution of sensory nerves. — Nearly every cell in 
the body, except in the epidermis and blood, is probably in connection 
with a sensory nerve, and, through it, is in touch with the central nerve 
cells. The endings of the nerves are so abundant in the skin just 
beneath the epithelium, that the point of a fine needle cannot be thrust 
in without producing pain. In the ends of the fingers they are more 
numerous than in any other part of the body. The muscles and internal 
organs have fewer sensory nerves than the skin, so that a cut may be 
continued into the deeper parts with but little pain. 

482. Kinds of sensations. — The cells are continually 
sending impulses to the central nerve cells telling of 
their needs, as of food or rest. These impulses often give 
rise to feelings which may seem to pervade the whole body. 
Then they are called coimnoii sensations. Some are pleas- 
ant and some are disagreeable. The natural unreasoning 
inclinations to gratify desires aroused by the needs of the 
body are i?istmcts. 

When something outside the body is acting upon the 
nerves it produces a feeling or impression of which a per- 
son is usually aware. By means of these sensations the 
mind forms definite ideas of the surroundings of the body, 



NERVES 269 

and so the feelings are called special sensations. Unlike 
common sensations, the meaning of the sensations must 
be learned. 

483. Common sensations. — Hunger, thirst, and fatigue 
are the usual common sensations felt by the mind. 
Hunger seems to be located in the stomach. If a sub- 
stance swallowed is not nutritious, hunger soon returns, 
even if the organ is filled full. On the other hand, if 
nutritious food is introduced into the body through the 
intestine, the feeling of hunger will pass away, even 
though the stomach remains empty. Some persons suffer- 
ing from indigestion are always hungry, though they eat 
enormously. But the food is not digested, and does not 
reach the cells, and there is always a feeling of hunger. 

Tliirst seems to be located in the mouth. Moistening 
the mouth allays it but for a moment only, while if water 
is introduced into the intestine or veins, the thirst disap- 
pears, even though the mouth receives no water. 

The amount of common sensations is small compared 
with similar impulses w^hich we do not feel. Every cell 
is continually sending tiny messages of its needs, and the 
central nerve cells promptly respond. 

484. Special sensations. — Knowledge of the outside 
world is gained by means of the touch, sight, hearing, 
smell, and taste. Of these, touch is located in all parts 
of the body, while special organs are needed to enable the 
nerves to catch the delicate impressions of sight, sound, 
smell, and taste. 

485. Sensations of touch. — When an object touches 
the epithelium of the skin, it causes an impulse to travel 
to the central nerve cells as a sensation either of touch, 
temperature, pain, or weight. All these sensations are 
included under the general term of toiich. Touch proper 



270 APPLIED PHYSIOLOGY 

is a slight sensation caused by contact of the skin with an 
object. By means of it such ideas as those of shape, 
smoothness, size, and dampness are gained. 

Different parts of the body vary greatly in the ability of their nerves 
to detect slight differences between two sensations. Thus the ends of 
the fingers distinctly feel two points j\ inch apart as separate points, 
while if two points are applied to the back, they seem as one point 
until they are separated two inches. So we naturally use the ends 
of the fingers to feel with. 

486. Sensations of temperature. — In the skin special 
nerves seem to end in minute points which are situated 
from -^Q to ^ of an inch apart. When these are touched, a 
sensation of heat or cold is felt, while the skin between 
feels only a touch or pain. Some spots give a sensation 
of cold only, and others of heat only. 

Sensations of extreme heat or of extreme cold cease to be feelings of 
temperature, but are felt only as pain. The skin is so sensitive that it can 
detect a difference of ^ of a degree of temperature between two objects. 

487. Painful sensations. — A sensation of touch or of 
temperature, if greatly increased or often repeated, be- 
comes unpleasant and is called a pain. The same sensa- 
tion may be felt at one time as a pleasant touch and at 
another as a pain. When an influence is becoming great 
enough to endanger the body, it arouses the nerves of 
pain and produces a strong and unpleasant feeling which 
overpowers the simple sensation of touch and compels us 
to withdraw from the danger. Pain is a protection for the 
body and not altogether an evil or a punishment. When 
the nerves of pain in an arm or leg are diseased, the 
limb may be burned beyond recovery without a person's 
knowledge. In many diseases pain is a prominent symp- 
tom, and the physician is besought to give it relief. Yet he 



NERVES 271 

hesitates before giving morphine, knowing that to relieve 
the pain is to mask the danger signals so that he cannot 
judge of the real cause of the trouble. 

Tickling is a sensation between touch and pain. It is produced in 
parts which are poorly supplied with nerves of touch, as on the back or 
the neck. At first, tickling is a pleasant sensation, but if continued, 
it becomes extreme suffering. Some persons and animals who are able 
to endure great pain are unable to control themselves when tickled 

Itching is a sensation which is overcome by producing a greater 
sensation in the part, as by scratching. Although itching is usually 
only an annoyance, in a greater degree it is a torment even worse than 
pain, and may lead a person to injure the skin seriously by deep 
scratching. 

488. The muscular sense. — Sensations of weight or of 
resistance are judged partly by the amount of muscular 
effort needed to move the body, and so depend in large 
part upon the motor nerves. But the feelings of pressure 
upon the body and of muscular effort aid in producing the 
sensation. An object lifted seems distinctly heavier if its 
weight is increased only -^^y, while if it is placed upon 
the skin, its weight m.ust be increased ^ before it feels 
heavier. 

489. Necessity of epithelium. — The covering of epithelium 
not only protects the nerves from injury, but also modifies an impulse 
which produces a sensation, so that it is spread over a larger area of 
nerves and is made a gentle instead of a painful sensation. 

490. Motor nerves. — Besides touching a sensory nerve, 
each cell probably communicates with a motor nerve also. 
Motor nerves begin at the central nerve cells and end at 
the cells of the body. Over them the central nerve cells 
send orders based upon information brought by the sen- 
sory nerves. Many orders are sent by willful efforts of a 
person, but by far the most are sent without our knowledge. 



2/2 APPLIED PHYSIOLOGY 

Motor impulses are of three kinds, — for motion, for 
secretion, and for growth. 

491. Impulses producing motion. — The action of every 
muscle cell depends upon an impulse brought from the 
central nerve cells by its motor nerve. When these influ- 
ences are cut off, there is paralysis of the part, so that no 
amount of willful effort can cause the muscles to move the 
limb. The peristalsis of the intestine and the beating of 
the heart are caused by influences brought to their muscle 
cells by motor nerves. Orders for movements of which 
we know nothing are far greater in amount than those 
sent to voluntary muscles. 

492. Impulses producing secretion. — Secretion is also 
dependent upon orders brought to the glands by motor 
nerves. For example, when food is taken into the mouth, 
the sensory nerves carry the news to the nerve cells, which 
at once send out an order along the motor nerves to the 
salivary glands to produce more saliva. If the nerves are 
cut, only a little saliva will be produced, while if the end 
in connection with the gland is irritated, the gland will 
respond with a greater quantity of saliva. In the same 
way the secretion of all glands is controlled. 

493. Influences producing growth. — When the motor 
nerve to a part is cut, the cells will be inactive, and, as it 
were, too lazy even to eat. So, unless continually under 
the influence of motor nerves, the cells become weak and 
waste away. When the cells of a part are much used, 
impulses are sent causing them to take in more nourish- 
ment, so that they increase in size and strength. Thus a 
muscle becomes larger and stronger by use. During the 
action of a muscle its motor nerves also bring orders for 
the arteries to dilate and carry more blood to feed the 
working part. 



NERVES 273 

494. Rate of transmission of nerve impulses. — Ordinary 
sensations travel about 100 feet per second. This is about the rate of 
the fastest express trains, but our arms are so short that pain seems to 
follow an injury instantly. In some diseases the rate is very much 
retarded, so that if the hand should happen to rest upon a hot stove 
it would be badly burned before the sensation would travel to the brain 
and give warning of the danger. 

495. A sensation traveling over a nerve seems to come from its 
beginning. When the funny bone, or nerve that winds around the 
back of the elbow, is pinched, the little finger side of the hand, where 
the nerve ends, feels as if pricked by needles. When an arm or a leg 
is cut off, and the nerves in the stump are irritated, a pain is felt which 
seems to be in the lost limb. When a nerve is pressed upon, it may 
be partly paralyzed for a while. Then the part which it supplies 
becomes less sensitive and is moved with difficulty. At the same 
time an impulse caused by the irritation of the pressure produces a 
sensation which seems to the brain to come from the end of the nerve. 
Thus when sitting crosslegged the foot often seems asleep and full of 
needles, while it is itself insensitive when touched. 

A ait nerve will become whole again, but it takes some weeks. In 
the meantime the parts supplied by the nerve cannot feel or move. 

496. Diseases of the nerves. — Nerves may become inflamed, 
producing the disease called neuritis. Then there will be great pain and 
tenderness over the entire course of the nerve. In severe cases there will 
be paralysis and loss of feeling. The disease is very slow in its course. 

Sciatica is a mild but painful form of inflammation in the main nerve 
of the leg. Inflammation of the nerves may be caused by rheumatism or 
malaria, but, above all, by alcohol. 

497. Effect of alcohol upon nerves. — A little alcohol 
seems to hasten the rate of transmission of nervous im- 
pulses by increasing the circulation of the blood, but a 
few drinks retard their action. A great danger of using 
alcohol is that it may cause neuritis or inflammation of the 
nerves. Slow, steady drinking may produce it as well as 
occasional sprees. It comes without warning, but remains 
a long while, producing pain and paralysis. Alcohol pro- 
duces the disease as often as all other causes combined. 

OV. PHYSIOL. — 18 



274 APPLIED PHYSIOLOGY 

SUMMARY 

1. The cells of the body are made to act harmoniously by 

means of orders sent from a few cells in a central 
nervous system. 

2. A nerve is a bundle of microscopic threads, each run- 

ning from a central nerve cell to the cells of the 
body. 

3. Nerves transmit impulses caused by irritation from out- 

side the body, and also impulses originated in either 
the cells of the body or the central nerve cells. 

4. Sensory nerves carry from the cells news concerning 

a substance which is touching the body, and they 
inform the central nerve cells when the cells are tired 
or are in need of food. 

5. Motor nerves carry orders to the cells to move, to 

secrete, to eat, and to grow. 

6. Impulses in nerves travel about 100 feet per second. 

7. Nerves may become inflamed and produce pain and 

paralysis. 

8. Alcohol often produces severe inflammation of the 

nerves. 

DEMONSTRATIONS 

116. Skin the leg of a small animal or frog, and push apart the 
muscles upon the inside of its upper part. White nerve cords will be 
seen to lie alongside the main artery and vein, and can be traced up- 
ward to the spinal cord and downward until they become lost in the 
skin or muscles. Notice that those which branch off to the skin are as 
large and numerous as those which supply all the rest of the leg. 
Notice how much force is needed to break one of the nerves. In 
ancient times it was supposed that tendons and nerves were the same. 
Compare a nerve with a tendon to see their points of resemblance. 

117. To show the effect of irritating a nerve in its course, pinch a 
boy's funny bone. He will wonder how the sensation travels to the 



NERVES 275 

brain when he feels it go down to his Httle finger. Explain that it 
only seems to come from the finger, but does not go there. 

118. With a power of at least 200 diameters, show specimens of a 
nerve mounted for the microscope. In a specimen of nerve cut length- 
wise, notice the slender conducting fiber running down the middle of 
each thread and its thicker, clear covering of fat. In a specimen cut 
across the nerve, notice that the conducting fiber of each nerve thread 
appears as a central dot within a circle of the protecting fat. Notice, 
the fine connective tissue between the threads. Sketch the specimen. 

119. Show the difference in sensibility of different parts of the skin 
by touching it with the points of a pair of compasses Upon the balls 
of the fingers the points will seem separate even if near together, while 
upon the back they will seem one when separated two inches. 

120. Show that some parts of the skin feel sensations of temperature 
more than the others by drawing the point of a lead pencil slowly 
across the cheek. At intervals there will be felt a cold sensation, show- 
ing that a special nerve of temperature has been touched. 

121. Cut a nerve in a recently killed frog and separate it from the 
flesh for a short distance. After a moment, pinch the nerve, and 
the muscles will contract. 



REVIEW TOPICS 



Describe the essential parts of the nervous system. 
Describe a nerve. 

Explain the two results of irritating a nerve. 
Define and name the kinds of sensory impulses. 
Describe the sensations of touch, pain, temperature, 
and weight. 

6. Tell how the cells make known their wants. 

7. Show how epithelium aids the sense of touch. 

8. Name and describe the three kinds of motor impulses. 

9. Give the rate of transmission of impulses along nerves. 

10. Describe the effects of pressure upon a nerve ; of 

cutting a nerve ; and of disease of a nerve. 

11. Tell how alcohol affects a nerve. 



CHAPTER XXIX 



THE SPINAL CORD 



498. The first collection of central nerve cells is in the 
spinal cord. The spinal cord is a soft white cylinder of 
nervous tissue, about half an inch in diameter. It is 
securely hung in the upper two thirds of the tube formed 
by the bony rings of the backbone. It extends from the 
bottom of the skull to about the level of the lowest rib, a 
length of about eighteen inches. It is only about two 
thirds as large as its tube, and so is not likely to be injured 
by bending the backbone. 

499. The gray matter. — When the cord is cut across, 
the central part of its end shows the grayish outline of a 

butterfly surrounded by a 
thick layer of a whiter 
substance. The gray mat- 
ter is a collection of nerve 
cells, which give off nu- 
merous nerve fibers like 
the central fibers of ordi- 
nary nerve threads. The 
cells are about yoVo ^^ ^^ 
inch in diameter. Some 
of the nerve fibers com- 
municate with other cells 
of the cord, and some take coverings and become ordinary 
nerve threads. The whole is bound together by delicate 
connective tissue. 

276 




A thin slice from the spinal cord with the 
cells and nerves magnified 200 diameters. 

a cells in the gray matter. 

b fibers in the gray matter. 

c nerve threads in the white matter. 



THE SPINAL CORD 



277 



The spinal cells receive a part of every impulse from the 
sensory nerves, and take part in sending out motor impulses 
to the various parts of the body. 

500. The white matter. — The white matter is made up 
of nerve fibers which still retain their coverings. In fact, 
the white matter is simply a huge nerve. The nerve 
threads of the white matter adjoining the right and left 
sides of the gray matter are motor threads carrying im- 

FRONT SIDE 




Diagram of the action of each part of the spinal cord. 

pulses from the brain to the cells of the gray matter. The 
nerve threads outside of these and the threads behind the 
gray matter are prolongations of the sensory nerves of the 
body, some of which finally go to the brain, and others 
connect with the cells of the gray matter of the cord. 

501. Spinal nerves. — The spinal cord giv^es off thirty- 
one pairs of nerves through openings between the rings 
of the backbone. Each ner\'c is made of a sensory 
and of a motor part which soon unite into a single 
bundle in which the two kinds of nerves cannot be dis- 



278 



APPLIED PHYSIOLOGY 




Diagram of the origin of nerves in 
the spinal cord. 



tinguished. These spinal nerves supply the whole body 
below the neck. 

502. Action of nerve cells in voluntary motion. — The 

spinal cells do not originate impulses or act of their own 

accord, but they act only when 
ordered to do so by the brain 
or when the cells of the body 
express a need of protection, 
nutrition, or rest. When a 

a motor nerve root from the front part perSOU wishcS tO lift his hand, 
b senstrnervrroot from the back ^^^ brain SCuds an Ordcr tO 

part of the cord. thcsc ncrvc cclls, and they in 

c gray matter of the cord. . i i.i j ^i. 

d winte matter. tum scnd the ordcr over the 

nerves to the muscles which 
move the hand. In this way the mind sends all orders 
for voluntary motion. For each muscle there is a sepa- 
rate group of spinal cells. If these cells are injured or 
destroyed, a person cannot move his muscles voluntarily. 




Diagram of reflex action. 

a tack pricking the hand. b sensory nerve. c nerve cell in the spinal cord. 

d motor nerve. e muscle moving the hand. 



503. Reflex action. — The spinal cells also send out 
orders in response to impulses brought by sensory nerves. 
Motor impulses sent in response to influences brought by 



THE SPINAL CORD 279 

sensory nerves are reflex acts. Reflex action is designed 
to protect the body from injury and to supply its needs. 
Most acts of the cord are reflex. When the finger touches 
a hot object, the sensory nerves carry the sensation to the 
cells of the spinal cord and to the brain. Before the sen- 
sation reaches the brain, the spinal cord sends out an order 
for the muscles to move the finger away from the heat. 
The brain becomes conscious of the burn and of the move- 
ment of the finger at about the same time. In this way 
the spinal cord protects the body against all kinds of 
injuries. 

504. Reflex action in relation to nutrition. — Digestion 
is mainly a reflex act. ]\Iotor impulses for glands to pro- 
duce the digestive juices are sent out from the spinal cord 
when the sensory nerves bring word that food is present 
in the stomach or intestine. Peristalsis is also a reflex act 
dependent upon the presence of food. The sensory nerves 
also carry to the spinal cells news of the temperature of 
a part and of its need of more or of less blood, and, in 
response, the cells send out motor impulses for the arteries 
to change their size. The heart is also somewhat affected 
in a reflex way. The sensations of exertion and fatigue 
are carried to the spinal cells, which send out orders for 
more rapid heart beats. Fear, joy, anger, and sorrow all 
affect the heart in a reflex way. 

The growth of each separate cell is controlled by the same set 
of spinal cells that produce motion in a part. Muscle cells, especially, 
need the constant stimulus of the spinal cells to keep them growing, for 
otherwise they slowly waste away and become weak. The spinal cord 
is continually overseeing the nutrition and growth of cells, and if it 
were to cease its oversight, their death would soon take place. 

505. Reflex action in habitual movements. — The reflex 
action of the cord aids in performing simple movements of 



28o APPLIED PHYSIOLOGY 

the body. The peculiar sensations which tell a man that 
he is beginning to fall pass to the cells of the cord, and 
they in a reflex way send out the proper orders for the 
muscles to put the body in an upright position again. 

506. Reflex action in education. — The reflex action of 
the spinal cord can be educated. Even a simple reflex 
action like standing must be learned. When a baby first 
tries to walk, his brain cells give the proper orders to the 
cells of the spinal cord, and they in turn give them to the 
muscles. Thus he slowly directs each detail of the move- 
ments with his brain. Soon the spinal cord learns to send 
the next order as soon as it feels the sensation of the 
previous movement, and finally all the movements needed 
become reflex, and the child runs about with but little 
effort on the part of his brain. 

In learning to play a piano, the brain is occupied both in reading 
the notes and directing the movements of the fingers in playing. 
But, at last, the brain has only to read the notes to the cord and it 
instantly sends the proper orders that they be played. 

Education and skill in any art consist in the ability of the cord to 
execute proper movements while the brain is wholly occupied with the 
design. In this ability to acquire new uses, the cells of the nervous 
system differ from all other cells of the body. When the hand is 
educated, it is really the spinal cells which are educated. 

507. Excessive reflex action. — Reflex acts are some- 
times not beneficial. A slight noise gives some people a 
fright, and in lockjaw the slightest sensation causes the 
spinal cells to send out orders for the muscles of the body 
to contract violently. Self-control is largely the power 
which the brain has of restraining the spinal cells from 
sending out orders even when strong and sudden sensa- 
tions are received. Thus, when something tickles the 
throat, it is possible for the brain to restrain the spinal 



THE SPINAL CORD 28 1 

cells from sending the order to cough. In the same way 
men sometimes endure great pain without shrinking. 

508. Broken back. — Injuries to the backbone may 
injure the spinal cord so that it cannot conduct nervous 
influences past the injured point. Then parts of the body 
below the point of injury can neither send nor receive 
messages from the brain, but are paralyzed both in sensa- 
tion and motion. Yet the reflex action of the part may 
persist, for the part of the cord below the injury still 
retains its vitality. 

509. Disease of the spinal cord. — There are diseases 
which may destroy the action of any single part of the 
cord or of the whole cord below the seat of the disease. 
Then there will be loss of sensation or of motion or 
impairment of nutrition, usually in the lower part of the 
body. The diseases are generally slow in their course and 
incurable. 

510. The action of the cord is unconscious. — The cord 

always acts wholly without a person's knowledge. Like a faithful 
nurse, it stands guard over the cells of the body and controls them in 
their nutrition, growth, and work. The brain restrains its excessive 
action and directs it in ordering the voluntary movements, but leaves 
to it almost the entire care of individual cells. 

SUMMARY 

1. The spinal cord is made up of a central mass of gray 

matter surrounded by white matter. 

2. The gray^ matter is made up of cells from which nerve 

fibers extend both to the brain and to the cells of the 
body. 

3. The white matter is composed of nerve threads which 

connect the cells of the cord with the brain and with 
the nerves of the body. 



282 APPLIED PHYSIOLOGY 

4. Thirty-one pairs of nerves connect the cord with all 

parts of the body. 

5. The use of, the cells is to send orders over the motor 

nerves when told to do so by the brain, and also 
to send orders in response to information brought 
to them by sensory nerves. 

6. Orders sent in response to sensations are reflex acts. 

7. Reflex acts are for protection, nutrition, and to relieve 

the brain from the drudgery of sending orders for 
every detail of bodily movements. 

8. The reflex action in an educated spinal cord enables a 

person to work with skill. 

9. Restraint of excessive reflex acts constitutes self-control. 

DEMONSTRATIONS 

122. Procure a spinal cord at the butcher^s. Notice the nerves 
going off from the cord. Notice how the cord is enveloped by a thick, 
fibrous sheath and is held in place by the nerves and fibrous bands. 
Remove the cord from the bone and slit open its sheath. Notice the 
soft consistency of the cord and its shape like two cords pressed 
together. On its clean-cut edge notice the grayish butterfly-shaped 
center and the pure white outer part. 

123. Examine a thin cross section of the cord under the microscope 
with at least 200 diameters. In the outer parts of the specimen notice 
the round circles of cut nerve threads. Explain that this is the white 
matter of the cord. 

Examine the central part, noticing the large nerve cells and nerve 
fibers which run in all directions. Notice the fine and wavy connective 
tissue fibers binding the whole together. 

124. The pure reflex action of the cord can be shown with a decapi- 
tated frog. Place a small piece of blotting paper, wet with a strong 
acid, upon its back, and it at once kicks it off with its hind leg. Prick 
its back, and it makes one leap. Suspend it with its hind legs hanging 
down, and let a toe touch a dish of acid, and it at once draws up the 
leg. (See demonstration 35.) 

Explain that the frog has no feeling or sense, but performs the move- 



THE SPINAL CORD 283 

ments in a reflex way to escape clanger in the same way that a boy 
suddenly jumps when he touches a sharp pin. 

125. To show reflex action, have a boy sit with one knee crossed 
over the other and hanging perfectly limp. Now strike the front of 
the knee just below the patella. The thigh muscles will contract and 
cause the leg to kick. This will succeed best if the boy is not looking 
when you strike. 

REVIEW TOPICS 

1. Describe the spinal cord ; its appearance and situation ; 

its gray matter, its white matter, and the origin of 
the nerves which arise from it. 

2. Describe how the cells of the gray matter act in caus- 

ing voluntary movements, and in causing reflex 
movements. 

3. Explain how reflex action is a protection to the body ; 

how it controls all processes of the growth and secre- 
tion of the cells ; and how it enables a person to 
acquire skill in movements. 

4. Explain how reflex acts may be harmful; how self- 

control may overcome the harm. 

5. Describe the effects of injury to the spinal cord. 

6. Describe the effect of diseases of the spinal cord. 



CHAPTER XXX 
THE SYMPATHETIC NERVOUS SYSTEM 

511. Of what the system consists. — The spinal cord con- 
trols the contraction of the arteries, the peristalsis of the 
intestine, and the growth of cells. Yet the impulses which 
it sends out for these purposes pass through another set 
of nerve cells and nerves called the sympathetic nervous 
system. 

The sympathetic nervous system consists of small bodies 
like grains of corn or smaller, called gaiiglia, from which 
nerves go out in all directions. There are four main pairs 
of ganglia in the head, and twenty-three in a row down 
the front of the backbone all connected by nerves. Each 
ganglion is a collection of nerve cells and nerve fibers 
bound together by connective tissue. Nerve threads con- 
nect its cells with the cells of the spinal cord and also with 
the muscle cells of the arteries and intestine. Through 
the arteries they probably affect all the cells in the 
body. The nerve threads are smaller than those of ordi- 
nary nerves, and seldom form bundles large enough to be 
seen. They usually consist of a fiber like the central fiber 
of an ordinary nerve thread without its fatty covering. 
They are thus not easily found even with the aid of a 
microscope. 

The nerves from the ganglia run mainly along the 
course of the large arteries. Upon the aorta and its 

284 



I 



THE SYMPATHETIC NERVOUS SYSTEM 285 

main branches in the chest and abdomen, nerves and small 
ganglia form intricate networks, each called a plexus. 

Just back of the stomach there is a large and important 
plexus called the solar plcx?is, whose nerves supply the 
muscles of the organs of the abdomen. A plexus within 
the heart controls the action of the heart. 

512. Sensory sympathetic nerves. — The sympathetic 
nerves carry both sensory and motor impulses, but only 
faint impulses of pain and touch. Thus the circulation 
of the blood and digestion of food go on almost without 
our knowledge, but a very strong irritation may give rise 
to an abdominal pain, as in colic. 

Sensory impulses telling of the wants of the cells and of 
the need of secretion or movements of the arteries or digest- 
ive organs are continually being received by the ganglia. 
These impulses travel slowly and require some time to 
produce an impression. Most of them travel only to the 
cells in the gangha, and few get farther than to the cells 
in the spinal cord. Only very strong impressions, whose 
cause may injure the body, reach the brain and produce a 
feehng of pain, hunger, thirst, or fatigue. 

513. Motor sympathetic nerves. — The ganglia send 
orders to the epithelial cells of the glands to produce 
their secretions, and to the muscles of the intestine and 
arteries either to contract or to dilate. They do this in 
response to information furnished by the sensory nerves. 
They also send out orders for the growth and nutrition 
of the cells of the body on receipt of news of their needs. 
Most orders from the ganglia are reflex. 

514. Mode of action of the ganglia. — If cut off from connec- 
tion with the cord, the ganglia send few impulses. The cord seems 
to furnish them with a supply of nervous energy. They seem to take 
a small amount of its active impulses and transform it into a large 



286 APPLIED PHYSIOLOGY 

amount of gentle impulses for the arteries and intestine. When poisons 
or spoiled food irritate the intestine to a dangerous degree, the sensa- 
tion goes beyond the ganglia and excites the spinal cells to action. In 
response they send out direct orders which cause energetic and painful 
peristalsis to remove the food, in marked contrast with the gentle action 
caused by the ganglia alone. 

515. Influence of the brain. — The brain has some power over 
the ganglia. Excitement or fear may influence the spinal cord so that 
it in turn modifies the impulses going through the ganglia. Sorrow 
seems to depress the ganglia so that the processes of digestion and 
assimilation are not so well performed, and the nutrition and growth of 
the cells of the body are diminished. But nature has arranged that after 
leaving the brain, mental influences shall act through two sets of nerve 
cells before they can directly affect the nutrition of the body. Thus 
man's body is protected against injury from his ever-changing moods. 

516. Connection of organs with each other. — By means of 

the sympathetic system, a nervous influence in one organ is spread over 
all the rest. Because other organs seem to share in the sickness when 
one is deranged, the nerves controlling them are called sympathetic 
nerves. Thus, when one organ is deranged, the others act less strongly 
and impose less work upon the disabled part. 

517. Injury to sympathetic nerves. — The sympathetic 
nerves are less influenced by outside impressions than any 
other nerves in the body, and great violence is needed to 
impair their action seriously. Poisons which are swallowed 
or produced during disease may injure them so that the 
ganglia almost cease to send out their orders. Then life is 
endangered, and strong nerve stimulants like strychnine 
are needed. 

Aside from poisons, almost the only grave danger which 
may threaten the sympathetic system is a blow upon the 
abdomen or neck. A hard blow or great pressure just 
below the ribs may paralyze the solar plexus. The arteries 
then enlarge and hold so much blood that too little goes 
to the head and brain. So there is danger of sickness and 
of death. A blow upon the side of the neck may injure 



THE SYMPATHETIC NERVOUS SYSTEM 287 

the large ganglia which are situated there, as well as 
the large nerves near by, and make such a profound 
impression upon the heart that death may take place 
at once. Blows upon the neck or abdomen are always 
dangerous. 



SUMMARY 

1. The sympathetic nervous system consists of collec- 

tions of nerve cells called ganglia, and of both 
sensory and motor nerves which follow the course 
of the arteries. 

2. The cells of the spinal cord send impulses to the 

ganglia, and they in turn distribute them to the 
arteries and glands and to the organs of the chest 
and abdomen. 

3. The ganglia send orders only in a reflex way accord- 

ing to impressions received from their sensory 
nerves. 

4. The ganglia control the contraction and dilatation of 

the arteries, the peristalsis of the intestine, the secre- 
tion of glands, and the growth of the cells of the 
body. 

5. The ordinary sensory impulses conducted by the sym- 

pathetic nerves produce no feeling. 

6. The heart is controlled mainly by a set of small ganglia 

within its own walls. 

7. The sympathetic system produces slow and gentle 

movements in contrast with the quick and active 
movements made by the spinal cord. 

8. The brain has no direct control over the ganglia. 

9. Blows upon the neck or abdomen may injure the sym- 

pathetic nerves so as to cause death. 



ZSS APPLIED PHYSIOLOGY 



REVIEW TOPICS 

1. Describe the sympathetic nervous system: its ganglia, 

nerves, plexus, and its connection with the spinal 
cord. 

2. Describe the sensory impulses of the sympathetic 

nerves. 

3. Describe its motor impulses and their relation to the 

arteries ; to secretion of glands ; to peristalsis ; to 
the growth of cells, and to the heart. 

4. Describe how the ganglia send out their impulses. 

5. Describe how the spinal cord has influence over the 

ganglia, and how they work independently of the 
cord. 

6. Describe how the brain can affect the ganglia. 

7. Describe how the action of the ganglia may be seriously 

impaired by injuries. 



CHAPTER XXXI 

THE BRAIN 

518. General structure. — The brain is the part of the 
central nervous system which can originate orders in dis- 
tinction from the spinal cord, which acts only in response 





Brain of a frog ; top view (X lo) . 
a cerebrum. 
b optic tubercles. 
c cerebellum. 
d medulla. 
e upper end of spinal cord. 



Brain of a hen ; side view (X 2). 
a cerebrum. 
b optic nerve. 
c optic tubercle. 
d medulla. 
e cerebellum. 
f spinal cord. 



to impulses brought to it. In reptiles, toads, and frogs, it 
is very simple in structure, but yet contains parts corre- 
sponding to all the parts of the brain of man. In them the 
spinal cord swells out to form a cone-shaped body called 

Above it there is a small flat 
ov. PHYSIOL.— 19 289 



the medulla oblongata 



290 APPLIED PHYSIOLOGY 

swelling called the cerebellum^ the next two smaller bodies 
called the optic tubercles, and at the top two larger bodies 
which together are called the cerebrum. They follow 
each other in a straight line. In man the parts are bent 
upon each other, while the cerebrum is so large that it 
covers all the other parts. 

519. Coverings. — The brain of man is a very soft body 
weighing about fifty ounces. It is contained in the top of 
the skull. It is covered with a delicate network of fibers 
called the pia mater, which carries the numerous blood 
tubes of the brain. Outside of the pia mater is a 
thick, tough membrane called the dura mater. The dura 
mater is the periosteum of the inside of the skull. 

520. The medulla. — The upper end of the spinal cord 
becomes enlarged into a wedge-shaped body called the 
medulla oblongata, or simply the medulla. The medulla 
is about one inch and a quarter in length and three quarters 
inch in breadth at its upper end. Its center is gray matter 
covered with white matter, both of which are direct con- 
tinuations of the same matter in the cord. 

521. Nerves of the medulla. — From the medulla there 
go out seven pairs of nerves to supply the head and face. 
They, together with five other pairs which the brain gives 
off, are called cranial nerves, in distinction from the spinal 
nerves. The cranial nerves which arise in the medulla 
are sensory and motor, and supply the head and face just 
as the spinal nerves do the rest of the body. They con- 
nect with cells in the medulla which act only in a reflex 
way. In this sense, the medulla is a part of the spinal 
cord, and not of the brain. One of these seven- cranial 
nerves is partly a nerve of the special sense of taste. 
Impressions of hearing, sight, and smell are carried by 
three cranial nerves arising higher up in the brain. 



THE BRAIN 29 1 

522. The vagus nerve. — One of the pairs of cranial nerves is 
called the 7'agus, or pneinnogastric^ nerve. It supplies a small sensory 
branch to the ear, and motor branches to the larynx and pharynx ; 
then it passes into the thorax and gives off branches to the heart, 
which restrain its action. It gives sensory branches to the esophagus 
and lungs, and finally reaches the stomach and liver. The main nerve 
supply of these organs is from the spinal cord, or from the sympathetic 
system, but the vagus nerve is an additional means for better regulating 
their action to suit the needs of the body. 

523. Centers originating impulses. — In the medulla, a 
collection of nerve cells, called the respiratory center, 
sends out a regular succession of orders for respiratory 
movements. While the orders may be hastened or re- 
tarded by other nerve centers to suit the needs of the 
body, yet the medulla compels the respiratory muscles to 
act so as to keep the body supplied with sufficient oxy- 
gen. Thus it is a real part of the brain. When the 
respiratory center is destroyed, respiration and life cease 
instantly. 

There is another part of the medulla, called the vaso- 
viotor center, which controls the contraction of arteries, 
and another which regulates the peristalsis of the esoph- 
agus in swallowing. While these are partly reflex acts, 
yet their perfect action requires original impulses to be 
sent from the medulla. 

524. Effects of reflex influences. — The respiration, circula- 
tion of the blood, and taking of food are essential vital processes of 
life which the medulla controls without our being aware of it. Strong 
influences from the nerves of the body may act in a reflex way to 
modify the impulses of the medulla. Great fear may cause the vaso- 
motor center to send out impulses for the contraction of the arteries so 
as to produce great paleness. Instances have occurred in which the 
disturbance of circulation from this cause has produced death. 

525. Effects of injury. — An injury to the respiratory and vaso- 
motor centers causes death at once. A broken neck, if high up, may 



292 



APPLIED PHYSIOLOGY 



involve the medulla and cause instant death. But the medulla is 
so situated that only the greatest violence can harm it. 

526. The cerebellum. — Just above and overhanging the 
medulla is a rounded mass called the cerebellum. It forms 



less than one fifth of the brain. 




r-« 



Diagram of a human brain. 

a cerebrum. b cerebellum. c medulla. 



It consists of an interior 
white mass of nerve 
threads, covered with 
a layer of gray matter 
about -j^-g- of an inch in 
thickness. On the sur- 
face are deep fissures 
into which the gray 
matter dips, so that its 
amount is greatly in- 
creased. In the gray 
matter are nerve cells 
which are connected 
with the rest of the nervous system through the nerves 
of its white matter. These nerve cells are the essential 
part of the cerebellum. They have no connection with 
any vital process of life, and do not take part in thought. 
A man with a diseased cerebellum can perform a single 
muscular act like raising his hand, but he cannot direct 
changing and complicated movements, such as are required 
in writing, walking, or balancing his body. Thus the cere- 
bellum acts like a balance wheel, so that orders for com- 
plicated movements may be sent with regularity and pre- 
cision. 

527. The optic tubercles. — The optic tubercles are two small 
collections of gray matter situated upon the main nerve tracts which 
connect the cerebrum and medulla. They seem to be connected with 
the reflex movements of the eye. Other collections of gray matter near 
them seem also to be connected with the eye. 



THE BRAIN 



293 




Cells from the gray 
matter of the cerebrum 
(X 300). 



528. The cerebrum. — The main nerve tract, after pass- 
ing through the spinal cord, medulla, and optic tubercles, 
spreads out to form a mass called the 
cerebrum. While in frogs and fishes it 
is no larger than the medulla or optic 
tubercles, in man it forms more than 
four fifths of the whole brain and over- 
hangs all the other parts. 

It consists of a central mass of nerve 
threads covered with a layer of gray 
matter one eighth of an inch in thick- 
ness, containing numerous large cells. Each cell gives off 
numerous fine fibers. Most of these fibers form an intri- 
cate network among the cells, but one from each cell takes 
a covering and becomes a nerve thread of the white mat- 
ter, and finally reaches other cells of the brain or even of 
the spinal cord. 

529. Fissures of the brain. — The cerebrum is divided 
nearly into two parts, called hemispheres, by a deep furrow 

running forward and 
backward upon the mid- 
dle of its upper surface. 
Another furrow, called 
the Sylviajt fissure, starts 
near the bottom of the 
fore part of the side of 
the cerebrum and runs 
backward and upward. 
Many other furrows and 
fissures from one quarter 
to one half inch in 
depth, run in waving lines between its main furrows, throw- 
ing its surface into folds called convolutions. The convo- 




Human brain cut crosswise. 



294 



APPLIED PHYSIOLOGY 



lutions increase the surface of the cerebrum, so that in all 
it measures about four square feet. This greatly increases 
the area over which the nerve cells in the gray matter may 
be spread. The interior of the cerebrum is a small irregu- 
lar cavity, called the ve7itricley which is filled with a clear 
liquid. 



^iJtegion- 




Regions of the head and action of the different parts 
of the brain. 



530. Regions of the cerebrum. — The fissures and con- 
volutions are nearly the same in all men, and mark out 
definite regions upon the surface of the brain. First, is 
the region just behind the forehead, called the frontal 
region. Second, is the region lying under the upper part 
of each side of the skull, and called the parietal region. 
Third, is the region about the ear, called the temporal 
region. It lies just above and in front of the ear. Fourth, 



THE BRAIN 295 

that part of the brain lying under the back of the skull 
is called the occipital region. Each region of the brain 
does a special work. 

531. Action of the cerebrum. — The nerve centers may 
act reflexively in response to sensory impulses, as the spinal 
cord usually does ; or automatically by originating their 
own impulses, Hke the respiratory center in the medulla 
and the nerve cells in the heart. The spinal cord, sym- 
pathetic system, medulla, and cerebellum all act in one or 
the other of these ways, and without our being conscious 
of their action. The cerebrum is the seat of the thinking 
mind. It acts in an automatic way, but we may be con- 
scious of any of its actions. It acts first by feeling sensa- 
tions; second by sending orders for voluntary muscular 
movements ; third, by thought. It does each kind of work 
in a particular region of its surface. 

532. Sensory regions. — Sensory impressions of which 
we are conscious are sensations. Sensations of hearing, 
smell, and taste are felt by the temporal region ; of sight 
by the occipital region ; and of touch by the parietal region. 
If either region is destroyed, the impressions going to that 
area are no longer received, and the person is devoid of the 
corresponding sense. Unless each impression reaches its 
own region of the surface of the brain, it produces no sensa- 
tion, although it may still reach reflex centers in the optic 
tubercles, medulla, or cord, and give rise to reflex action. 

533. Memory. — Impressions may be retained in the cells 
and be recalled. These constitute memories. Our memo- 
ries are complex stores of impressions in widely separated 
parts of the brain. The sum of our different memories 
constitutes a great part of our knozv ledge. 

Different regions of the brain are connected by nerve 
fibers. So when one region recalls a memory, another 



296 



APPLIED PHYSIOLOGY 



region recalls another memory of the same object. Thus, 
when the temporal region recalls the memory of a sound 

of a bell, the occipital 
region recalls its appear- 
ance. 

534, Motor regions. — 
Orders for voluntary mo- 
tion are sent by the cells 
lying just in front of a 
zone connecting the two 
ears. Each muscle of 
the body is controlled 
by a special set of nerve 
cells called its motor 
center. 



A motor impulse passes 
down through the white mat- 
ter of the cerebrum, medulla, 
and spinal cord to the spinal 
nerve cells, and then out along 
a motor nerve to a muscle. In 
an injury or disease in the top 
of the skull some of the cells of 
the motor region may be in- 
volved, giving paralysis of cer- 
tain muscles. By the muscles 
affected one can often judge 
of the exact location of the 
trouble and remove it by an 




Diagram of the course of nerve influences 
in voluntary motions. 

a object to be picked up. 

b sensory nerve. 

c the part of the influencfe which goes to the 

cells of the cord, and tends to produce 

reflex action. 
d cell of spinal cord. 
e motor nerve from spinal cord. 
/ continuation of the sensory nerve b up the 

cord to the brain. 
g cell of the brain which perceives touch. 
h motor cell. 
i thought cell. 
j motor nerve fiber running to the cells of the operation. 

cord, and carrying an influence which 535. Relation of the 

continues along the motor nerve ^. «^^«^«„ *.^ +t,« *««-«-/v*. -.-q 

k muscle which moves the hand. SCnSOry tO the HlOtOr rC- 

gions. — The motor and sen- 
sory regions are in close connection by nerve fibers in the white matter. 
The motor region regulates its impulses according to information brought 



THE BRAIN 297 

to sensory regions by sensory nerves. A carpenter regulates the force 
with which he pushes his plane according to the feeling of muscular 
resistance. 

536. Memory of movements. — Acts of motor cells are 
stored in memory and constitute a part of knowledge. 
All motions must be learned at first. When the brain 
centers have learned a movement thoroughly they teach 
the spinal centers so that finally their work is almost en- 
tirely relieved, and they can be occupied in other thoughts. 
Awkwardness is usually the result of the brain's attempt- 
ing to send out orders for motion while it is occupied with 
other thoughts. Ease and grace of motion come when the 
spinal centers have learned to relieve the brain center. 

537. Thought regions. — The cells of the frontal regions 
take note of memories stored in other regions, and by their 
comparison form new ideas. Thus, a pause between two 
sensations or mental acts gives rise to an idea of time ; 
and the sight of two objects removed from each other gives 
the idea of space and of number. Neither time nor space 
nor number in itself can make an impression upon the 
senses, and yet they are realities in the mind. Comparison 
of memories and the formation of new ideas is tJimking. 
Thoughts themselves are stored in memory and can be 
recalled and compared. 

538. Speech. — Thought is expressed by speech. By 
means of speech new sensory and motor ideas and new 
thoughts arc gained and stored in the memory without the 
cells of the different regions experiencing the particular 
sensations. Herein is the main difference between a man 
and an animal. An animal gains new ideas only by 
memory of its sensations and acts which it itself experi- 
ences, but a man can acquire them second hand by being 
told. Thus a man may be profited by the experience of 



298 APPLIED PHYSIOLOGY 

Others. Knowledge gained only by long and patient 
research of wise men is imparted to children in a few 
moments, while an animal can impart knowledge only in 
a limited degree. 

539. Speech in animals. — All animals have a variety of natural 
cries. Monkeys have a dozen separate cries which are similar in all 
species. A hen has at least five different cries to express as many 
different ideas. Parrots and crows have been taught to speak a few 
words, but they do it just as the mocking bird or brown thrush imitates 
any sound which it hears. Speech belongs to man alone. 

540. Of what speech consists. — Speech is one of the 
highest and most complicated of mental processes. It is 
not a natural gift, but must always be learned at first. 
A child first hears a word spoken. He records it in the 
temporal regions of the brain, and learns to recall certain 
sensory and motor memories when he hears the word. 
By the time he is a year and a half old his motor region 
begins to form the word when he thinks of the memory. 
At the age of six or eight he begins to recognize the printed 
word with his sight region, and finally he learns to write 
the word with his motor region. Thus nearly every region 
in the brain takes part in some form of speech. 

541. Center for spoken words. — The muscles of the 
mouth can be moved by the cells of the face center in the 
motor region, but their movements in speech are so precise 
and complicated that a center is especially provided to pro- 
duce their movements in talking. It is situated just below 
and in front of the motor area, but is usually upon only 
one side. When this center is disturbed, a person cannot 
talk, although he understands spoken and written speech, 
and has control of his lips and tongue in doing other things. 

542. Disturbance of the speech centers. — There are cases 

in which the word-seeing center is disturbed so that a person can 



i 



THE BRAIN 299 

speaK and write correct answers to questions, but cannot read and un- 
derstand what he has just written. Sometimes a person cannot speak 
his thoughts, but can read aloud what he has written. Careful observa- 
tion of the speech is of great value in locating brain diseases, for the 
speech centers involve nearly every region of the brain. 

543. Mind study. — The cerebral cells act in as definite 
and uniform ways as the cells of the intestine or heart, and 
men studied the laws of their minds long before the struc- 
ture or even the existence of cells was known. The actions 
of the mind are divided into three great divisions. First, 
is the i7itellcct, or the pure knowledge-gaining faculty. This 
includes the work of all the sensory regions of the brain 
and such a part of the frontal regions as is concerned in 
receiving knowledge through speech. It is the basis of the 
other mental acts. 

544. The sensibilities. — The second division of mind 
study comprises the sensibilities, or the feelings. Much 
of knowledge does not concern us in the least. All feeling 
is based on knowledge, and all knowledge leads up to 
feeling as we come to know a thing intimately. We love 
it or hate it, and are sorry for its loss. 

545. The will. — The third and highest act of the mind 
is to will to do. It is the control which the frontal region 
has of the motor region. In order to do a thing we must 
first have knowledge, and, second, we must feel some degree 
of emotion or desire to do it. Only a small part of knowl- 
edge causes feeling or emotion, and only a small part of 
even our strong feelings are expressed in action. 

Of all the actions of the mind the will is the most difficult to arouse 
and control. Since it depends upon feeling, this faculty must first be 
aroused. Men readily act their feelings of anger and fear. To form a 
new will, active and brave, which is capable of controlling the natural 
and acquired appetites and passions, is the highest and noblest work 
of man. 



300 



APPLIED PHYSIOLOGY 



546. Brains of animals. — The medulla is much the same in 
all animals from the frog up to man. This is because breathing and the 
flow of blood are much the same in all. The cerebellum in a frog or 
snake or fish is very small, for they need but a small regulating and 
balancing part. A bird or a hen must make precise movements in 
balancing itself in flying or roosting, and so it has a large cerebellum. 




Brain of an ox. 
a outline of brain in the skull. b the brain removed from the skull. 



The optic tubercles of frogs and birds are well developed, for their eyes 
are perfect. The cerebrum of frogs and snakes and fishes is very small. 
Its hinder parts are the largest, for in them the impressions of sight, 
hearing, and smell are located. Its fore parts are mere points, as would 
be expected from the low intelligence of the animals. A bird has a 
larger cerebrum, corresponding to a greater mind. An animal's cere- 
brum is much larger and is somewhat folded to give room for more 
nerve cells, but the frontal or thouMit region is small. An animaPs 



THE BRAIN 3OI 

senses are as acute as a man's, and so the back parts of its brain are 
well developed. 

547. Animal intelligence. — An animal is capable of storing 
sensory and motor impressions in memory, and of sending out motor 
impulses according to sensory impressions. In some respects he is 
capable of doing this to a far greater extent than man. For instance, 
a dog can find his master by the sense of smell alone. He can also 
use his frontal region in thought and judgment, but to an extent which 
corresponds to the small size of this region. 

548. The essential difference between man and animals. — 

The possession of speech seems to be the key to man's progress and 
noble ambitions. By means of it the Creator has revealed to him a 
knowledge of things before the foundation of the world, and of things 
to come. Animals are incapable of receiving instruction except through 
the senses and so they make no progress. Man rises in thought above 
time and space itself. 

549. The nervous system in lower animals. — All four- 
footed animals, birds, fish, and reptiles possess nerves, a spinal cord, 
and a brain. Their nerves, sympathetic system, spinal cord, and 
medulla are developed nearly as much as in man, for the creatures eat, 
feel, move, and breathe, often to a greater extent than man. The 
cerebrum is developed according to the intelligence of the animal, and 
the cerebellum according to the complication of its movements. 

Insects and worms and shellfish have no brain or spinal cord, but 
a row of ganglia like those in the sympathetic system extends through 
the body. Each ganglion gives off nerves to the cells of the body. 
These creatures do little else than eat and digest food, and hence the 
highest nervous system is not needed. 

In the lowest form of life there is no nervous system at all. When 
the animal consists of a few cells or of only a single cell, no nervous 
system is needed. 



SUMMARY 

1. The brain is the part of the central nervous system 

which originates impulses. 

2. The brain is continuous with the spinal cord, and 

consists of the medulla, cerebellum, optic tubercles, 



302 APPLIED PHYSIOLOGY 

and cerebrum. Each consists of gray matter con- 
taining nerve cells, and of white matter made of 
nerve threads. 

3. The medulla is like the spinal cord in that it gives off 

sensory and motor nerves. 

4. The medulla also originates impulses controlling res- 

piration and the contraction of arteries. 

5. The cerebellum adjusts the voluntary motor impulses 

of the brain, so that movements like balancing of 
the body are done with precision. 

6. The optic tubercles are reflex centers for the eyes. 

7. The cerebrum forms four fifths of the brain, and con- 

sists of a puckered covering of gray matter over a 
central mass of white nerve fibers. 

8. The cells of each part of the brain have a definite 

work to do. They receive sensory impressions, 
send motor impulses, and think. 

9. The impressions of each cell remain as permanent 

memories which can be recalled at will, 

10. By means of speech, thought, sensory and motor 

impressions are conveyed to other persons and there 
become memories as though they had actually been 
experienced. 

11. In speech the centers for motion, sound, and sight 

all take part. 

12. There is a special center for producing the movements 

of the mouth in speech. 

13. The first stage of mind action is knowledge ; the next, 

emotion ; and the third, willing and acting. 

DEMONSTRATIONS 

126. Show as types the brains of a frog or fish ; of a hen ; and of a 
fourfooted animal. A frog's, fish's, or chicken's brain can easily be 



THE BRAIN 303 

removed bv cutting away the skull. After opening the top of the skull, 
place it with the brain in Mliller^s fluid or formalin for a few days, when 
the brain will be hard and can be removed with little injury. 

127. In the frog, note the medulla, then the thin cerebellum, look- 
ing like a disk of paper with its edge inserted just above the medulla. 
Note the swelling optic tubercles, and then the long, pointed halves of 
the cerebrum. 

Next compare the same parts on a bird's brain. Note the similar 
medulla and optic tubercles. Note the large cerebellum forming a half 
moon above the optic tubercles, and marked with cross fissures upon 
its back part. Note the cerebrum in front, shaped like a chestnut and 
as large as the rest of the brain. 

Next compare the same parts in a mammal's brain. Note th^ similar 
medulla, but the larger cerebellum. The optic tubercles are obscured 
by the cerebrum. Note the cerebrum, large enough to cover almost 
all the rest of the brain. Note the convolutions. 

Now compare these brains with a model or a picture of the brain 
of man. Note the large frontal regions in man and the larger and 
more numerous fissures and convolutions, and that the cerebrum com- 
pletely covers all the other parts of the brain. 

128. When the skull of an animal is opened, note the lining of tough 
and thick dura mate}-, which may be peeled off with little difiiculty. 
Note that it extends in between the two hemispheres of the brain and 
between the cerebrum and cerebellum. Underneath it, note the deli- 
cate meshes of the pia mater ^ containing numerous blood tubes. Note 
that it dips into all the fissures and contains a small amount of a thin, 
clear fluid. 

129. Examine a specimen of the gray matter of the cerebrum or 
cerebellum with a microscope magnifying 400 diameters. Note its nerve 
cells with fine branches. The white matter will appear like a collection 
of ordinary nerve fibers. Sketch the specimen. 



REVIEW TOPICS 

1. Name the different parts of a frog's brain in order, 

and tell how they differ from the same parts in a 
man's brain. 

2. Describe the two coverings of the brain. 



304 APPLIED PHYSIOLOGY 

3. Describe the medulla, its nerves and reflex action ; 

its respiratory center ; its vasomotor center ; and 
the effects of its injury. 

4. Describe the cerebellum and give its action. 

5. Describe the optic tubercles and give their action. 

6. Describe the cerebrum ; its hemispheres, fissures, con- 

volutions, gray and white matter, and regions. 

7. Locate the region in which impressions of sight are 

received ; of touch ; of hearing ; of smell ; and of 
taste. 

8. Describe the region from which motor impulses for 

voluntary motion are sent out. 

9. Describe the memory, and show why recalling one 

thought brings to mind another thought of the 
same object. 

10. Locate the thought region of the brain, and describe 

the process of thought. 

11. Show that by speech man gains ideas which an animal 

can get only by actual experience. 

12. Locate and describe the mode of action of the center 

for spoken words ; for written speech ; and of the 
speech-hearing and speech-seeing centers. 

13. Describe the three main divisions of the acts of the 

mind. 

14. Compare the corresponding parts of the brains of 

different animals with each other and with the same 
parts of the brain of man. 

15. Describe the nervous system in insects, worms, shell- 

fish, and in the lowest forms of animals. 



CHAPTER XXXII 

INFLUENCES WHICH AFFECT THE MIND 

550. Stimulation to action. — The thought cells of the 
brain are given power over voluntary actions of the body, 
with no higher power to cause them to act, except the will, 
which is the result of their own action. Were a child left 
entirely to itself, it would probably exercise its mind no 
more than an animal. But the sight of objects and ambi- 
tions not yet attained spurs the thought cells to action, 
just as sensations cause the spinal cord and motor region 
to act. Without constant stimulus of the senses and feel- 
ings the thought cells languish and almost cease to act. 
As the body is compelled to grow by the cells of the spinal 
cord, so must the mind be compelled to grow by an effort 
of the will. Few men possess a will strong enough to act 
without the stimulus of other minds, but association with 
trained minds arouses the will to exercise one's own mind. 

551. Concentration of the mind. — In order to become 
educated, the mind must be exercised persistently and for 
hours at a time. The mind does not grow unless its whole 
energies are often directed towards a single object. It is 
not study to read a page and then to converse about sports 
for a moment and then to study another moment, for each 
impression sweeps away the preceding one. True study 
is to sit down in a quiet room, and to fix the mind upon the 
book continuously for an hour or more. Then the mind 
will be occupied so that it takes no note of time or outside 

ov, PHYSIOL. — 20 305 



306 APPLIED PHYSIOLOGY 

impressions. Any one will find study interesting if he will 
concentrate his mind upon a subject so that he gains 
knowledge. Then when playtime comes he will enter 
into the sport with zest and satisfaction. No one who has 
not been working can truly enjoy play. 

552. Persistence of mental impressions. — Brain work re- 
quires heat and energy like muscular work. The cells of the cerebrum 
retain an impression of each thought, which is deep and permanent in 
proportion to the power expended upon it. A lesson learned in a 
minute makes some impression upon the cells, but it is gone in another 
moment. A dull boy hammers away at a lesson by the hour, but at the 
end of a year he will have retained far more than the brilliant boy who 
loses his impressions as fast as he gains them. 

It is extremely difficult to efface impressions once really made upon 
the cerebral cells. Apparently, knowledge may be forgotten, but some 
day something will cause the cells to recall the impressions. Thus it 
is very important to avoid all thoughts which we should be ashamed to 
recall. 

553. Habit. — Memories of thoughts often repeated may 
arise in spite of the will to restrain them, and may compel 
the motor region to do acts which the will utterly abhors. 
At first a man's will has to direct the thoughts to speak 
profane words. Soon the words become so imprinted in 
thought that they arise even without his knowledge. 
Habits grow faster and stronger than the will to overcome 
them. On the other hand, one can form a habit of study 
and of mind cultivation so that mental work is a pleasure. 
The more one works with his mind, the more he enjoys 
his work. The mind is constantly forming habits of 
thought. Even if it thinks nothing bad, yet it may soon 
acquire a lazy habit of not thinking at all. 

554. Heredity. — Impressions of any kind may become 
so permanent that one's children have a tendency to 



INFLUENCES WHICH AFFECT THE ISHND 30/ 

acquire them. The son of a criminal has a natural 
tendency to become a criminal, and even if he is well 
brought up in an upright family he will be far more likely 
to yield to temptation than a well-born child. Children of 
educated parents take naturally to study. Children of 
excitable and nervous parents will also inherit their 
disposition. By education, natural tendencies of mind and 
character can be overcome. If a wrong tendency is known 
and is not corrected, the blame for future action of the 
child will lie with his educators rather than with the man. 

555. Unconscious mind action. — When the mind is intensely 
occupied it may not take note of severe sensory impressions. Thus 
soldiers in battle often fight on, unconscious of severe wounds. You 
may try in vain to recall a name. Later, when you are thinking of 
something else, the name may flash into your mind. You may strive 
to direct the mind to a lesson, but thoughts of a sick friend may persist 
in arising, and may shut out all thoughts connected with the study. In 
acquiring any new thought the mind must reason by conscious efforts, 
step by step, until the idea is clearly in view. Ever afterward the mind 
may reason out the steps unconsciously and almost instantly, so that we 
may lose sight of the complexity of the mental processes involved in 
forming the idea. Learning to perform any mental process is essen- 
tially becoming able to do it with little or no conscious effort. Then 
the mind, relieved of the conscious direction of thoughts already 
learned, is free to acquire new ones. Man is probably unconscious 
of most of the steps in his mental processes. 

556. Sleep. — It is as impossible for the mind to put 
forth conscious effort continually as it is for the mus- 
cles. A rest from conscious effort is called sleep. As a 
rule, a man needs about seven or eight hours of good 
sleep ; a boy of sixteen needs nine or ten hours, while one 
of six needs twelve. Sleep should be regular, so that the 
brain may not become excessively tired between times. 
As a general rule, an early hour both for going to bed and 



308 APPLIED PHYSIOLOGY 

for rising is desirable. If a student would go to bed when 
he feels sleepy, and would sleep an hour or two longer 
each night, he would feel able to do more and better work 
during his working hours. 

557. Sleeplessness. — Like other organs while resting, the brain 
contains but a small quantity of blood during sleep. If a large amount 
of blood continues to flow through it, sleep will be impossible. Often 
when a person cannot sleep he can feel the pulse in his temples throb 
and hear it as his head lies upon the pillow. 

A common cause of sleeplessness is an empty stomach. A light 
lunch will often cause the arteries of the abdomen to dilate and take up 
the blood which circulates in the brain and so relieve the cause of sleep- 
lessness. 

Lack of work during the day may be a cause of sleeplessness. Many 
a man finds himself suddenly unable to sleep when he retires from active 
business. It seems to be a law of nature that he who does not work 
cannot sleep, for he is not tired enough to need a rest. Occupation for 
the mind and body will give such persons a good night's sleep. 

Worry will also cause sleeplessness, for it keeps the cells of the brain 
in action just sufficiently to attract the blood to the head. The brain 
can endure extremely hard work if it only gets rest between times. 

Narcotics^ like opium and chloral, will always produce sleep if taken 
in sufficient doses. But they injure the cells to a greater degree than 
they do good. In times of anxiety the temptation to resort to them is 
great, but their use at such times invariably leads to a habit of using 
them, with all its accompanying evils and dangers. 

558. Dreams. — Sometimes during sleep the sensory and 
motor regions recall their memories with the vividness of 
real life. This is a di^eam. The thought regions rarely 
take part in a dream. Disordered memories of the sensory 
and motor regions seem to be realities, but in the absence of 
judgment they seem harmonious and natural, and we recog- 
nize their fantastic nature only when reason returns with 
the waking hours. Formerly dreams were supposed to be 
heralds of events to come; but now it is known that they 
are but the shadows of previous experiences. 



INFLUENCES WHICH AFFECT THE MIND 309 

559. Change of occupation. — When one set of brain cells 
has become tired, it is well to direct the thoughts to another 
subject and let the first set of cells rest. It is a relief to 
study a history lesson after working hard at arithmetic 
problems. A change of occupation is the best kind of 
rest. It is well to alternate pure brain work with work 
which, like gardening and carpentering, requires muscular 
effort. 

560. Healthy bodies. — The brain depends upon the blood and 
digestive organs for the power with which to work. When any of the 
organs are acting improperly the brain is the first to suffer. The strong- 
est brains are contained in the healthiest bodies. No kind of food is 
brain food more than another, but fish and phosphates are hardly so 
valuable as beefsteak and salt. 

561. Exercise and brain work. — Muscular exercise is needed 
to keep the body in the best physical condition. Thus it makes the 
brain stronger. It also takes some blood which otherwise would con- 
tinue to circulate in the brain, and thus it rests the mind after work. 

If exercise is continued until the body is tired, no energy is left for 
the brain, but sleep comes on as soon as the body composes itself for 
brain work. Exercise for the benefit of the brain should be brisk in 
order to produce the best eflfect upon the circulation of the blood, but 
it should never be carried to the point of fatigue. 

562. Nervousness. — When the brain is exhausted from 
overwork or from worry, it has not enough energy to con- 
trol itself or the reflex actions of the spinal cord. Slight 
and strong sensations are equally unpleasant, and the 
effort to control the feelings seems to increase the suffer- 
ing. Thus there arises a condition called nei-voiisness. 

Nervousness is a lack of self-control. The judicious ex- 
pression of sympathy by a strong-willed person is the best 
means of overcoming it. On the other hand, sarcasm and 
scolding only do injury and increase the nervousness. 

563. Hysteria. — An extreme lack of self-control is called 



3IO APPLIED PHYSIOLOGY 

hysteria. The person laughs or cries at trivial things. The 
motor and sensory regions often seem paralyzed. Persons 
may even wound themselves to inspire sympathy. Yet 
there may be most violent convulsive movements. A well- 
marked case closely resembles the actions of a spoiled child 
when his will is crossed. 

The treatment of hysteria is to arouse the will power. Expressions 
of sympathy only make the condition far worse. A firm and stern 
nurse can usually command obedience. Any sudden fright will gener- 
ally break up an attack. 

564. Insanity. — A persistent lack of control of the 
brain in one or more directions is called msanity. Ner- 
vousness often repeated and yielded to may become insan- 
ity. Worry and overwork are extremely common causes, 
while alcohol causes half the cases in asylums. Often the 
weakness of the brain cells is inherited. 

A person about to become insane is changed in dispo- 
sition and character. There is a lack of self-control and 
of judgment. Prompt rest and care of the body may over- 
come the attack, but a strong-willed friend will be needed 
to guide the treatment, for the patient thinks that every- 
body except himself is wrong. 

565. Forms of insanity. — In insanity there are no new mental 
traits or possessions by demons, as used to be supposed, but only an in- 
crease of some mental acts and a decrease of others. The expression 
an unbalanced mind well describes the condition. There are three 
main forms of its disturbance, giving rise to three forms of insanity. 

An increase or hastening of one or all mental acts sometimes takes 
place. The thoughts flow faster than words can express them, and so 
the talk is a meaningless gibberish. The senses are uncommonly alert, 
and one may think he hears and sees things which do not exist. He 
cannot understand why others are so slow and dull, and so is apt to 
show violent outbursts of temper. Yet although he may harm others. 



INFLUENCES WHICH AFFECT THE MIND 311 

he will seldom hurt himself intentionally. This condition is called 
maniiij and constitutes the popular idea of a crazy person. 

In a second form of insanity the thoughts flow slowdy. Questions 
are ans\vered in a hesitating way of which the person is conscious, so 
that he feels that he is incapable of doing business or even associating 
with men. He becomes gloomy, and imagines he has committed an 
unpardonable sin which he endeavors to discover. He reads his Bible, 
but imagines that all its curses apply to him personally. He finally 
tries to destroy himself so that he may no longer be a burden to his 
friends. This condition is called fuelancholia. 

A lueakening of the whole brain is the third form of insanity. De- 
generation of the brain cells often occurs in old people, and is commonly 
called softening of the brain. It may occur in middle age. Alcoholic 
drink is a common cause of the condition. 

566. Treatment of insanity. — Insane persons can usually talk 
and exercise some reasoning powers. A sympathetic nurse should win 
their confidence and control them by reason and persuasion. Special 
training is required to carry out proper treatment, and so it is usually 
best to remove them to an asylum. Most cases of insanity improve in 
from three to six months, and many permanently recover. 

567. Delirium of fever. — In poisoning, either by drugs or by 
the poisons of sickness, the mind is apt to be somewhat disturbed. 
Anything which diminishes the fever will quiet the mental disturbance, 
and with the end of the fever the mind regains its right state. In rare 
cases, the delirium persists, and is then a real insanity. 

568. Injuries to the brain. — The effects of a blow or 
other injury to the brain depend upon its situation. Any 
injury may cause unconsciousness. Injuries to the top of 
the brain impair the faculties situated in the injured regions, 
but seldom cause death. Injuries to the base of the brain 
are usually fatal by involving the medulla. After the ef- 
fects of the blow have passed off, a blood clot remaining 
may still cause paralysis of the cells of a particular part so 
that the person may lose certain mental powers.' 

569. Apoplexy. — The arteries of old persons sometimes 
become hard and brittle so that one is liable to burst in the 



312 APPLIED PHYSIOLOGY 

brain, especially in its motor region. Then the pressure 
of the escaped blood injures or destroys some of the brain 
cells. This constitutes apoplexy, or a stroke of paralysis. 
There is usually unconsciousness for a time, followed by 
paralysis of some limb and of speech. Recovery is usually 
slow and imperfect. If the medulla is affected, death 
quickly results. Confusion of speech, dizziness, and tin- 
gling in a limb usually precede an attack for some days. 
When a person is taken with a stroke of apoplexy, he 
should be kept very quiet, with his head raised, so that the 
blood will flow through the brain as gently as possible. 

570. Fits. — If the cells of the motor region of the brain are irri- 
tated, as by a sliver of bone or a blood clot, they may send impulses at 
intervals to produce violent movements of the muscles. This is called 
a convulsion or -a. fit. An operation for the removal of the substance 
which presses upon the cells will relieve the fits. 

In young children, irritation of indigestible food in the intestine or 
of the poisons of fevers may cause the spinal cord or motor region to 
send out reflex orders and so produce a convulsion or fit. Convulsions 
in a child can be stopped by immersing it in a tub of very warm water. 
Then something to clear out its intestine should be given so as to re- 
move the cause of the convulsions. In all forms of convulsions there 
is little suffering, for the person is wholly unconscious. 

Convulsions may come without warning and produce entire uncon- 
sciousness for a minute or two, when they cease, and the person is ap- 
parently none the worse for it. This trouble is called epilepsy or fits. 

During the fit there is no danger except that a person may bite his 
tongue. So the only thing to be done is to stuflf a handkerchief into 
his mouth so as to crowd the tongue away from the teeth. Excitement 
is liable to bring on fits in a person subject to them- 

571. Panics. — In times of bodily or financial danger, where many 
are assembled, a single person may infect the whole audience with an 
insane fear. Then each person thinks only of his own safety, and 
many are sure to be trampled upon and injured. In such a time a 
single cool head will do much to calm the excitement. Fire drills in 
school teach the pupils to be orderly in the face of danger. 



INFLUENCES WHICH AFFECT THE MIND 313 

SUMMARY 

1 . Constant effort of the will is needed to keep the thought 

cells of the brain acting. 

2. A few repetitions of either good or bad acts produce 

habits of doing them. 

3. Many mental acts are done wjthout consciousness. 

4. In sleep the thought cells rest from work and there is 

complete unconsciousness. Lack of mental occupa- 
tion during the day, worry, and an empty stomach 
are common causes of sleeplessness. 

5. A change of occupation is rest for the mind. 

6. Active exercise, short of fatigue, improves the mind 

as well as the body. 

7. A lack of self-control when irritated by slight sensa- 

tions is nervoiLsness. An extreme lack of will power 
is Jiystc7'ia. 

8. A persistent lack of control of the thoughts is 

insanity. The thoughts may either be hastened, or 
hindered, or suppressed, giving rise to three forms 
of the trouble. 

9. In fevers there is often a temporary delirium which 

resembles insanity. 

10. In old people, an artery of the brain sometimes bursts, 

and the clot, pressing upon the nerve cells, stops 
their action and produces a shock of apoplexy. 

11. Irritation of the motor region may cause the cells to 

send orders for violent muscular movements, pro- 
ducing a fit or convulsion. 

REVIEW TOPICS 

I. State how^ the cells of the cerebrum differ from the 
other cells of the body in regard to being controlled 
and made to act. 



314 APPLIED PHYSIOLOGY 

2. Tell how best to study. 

3. Discuss persistence of impressions ; habit ; heredity. 

4. Show how the mind acts without our knowledge. 

5. Tell the nature of sleep; its use; how much is 

required ; and when to sleep. 

6. Tell how sleeplessness is produced by an empty 

stomach ; by worry ; and by lack of work. 

7. Tell the nature of dreams and of what ideas they 

usually consist. 

8. Show how a change of occupation rests the brain. 

9. Show that good health is needed for good brain work, 

and tell how exercise affects the brain. 

10. Show the nature of nervousness, and of hysteria, and 

tell how to overcome them. 

11. Give the causes of insanity, its three forms, and its 

treatment. 

12. Give the result of blows upon the brain. 

13. Give the nature of a stroke of apoplexy, and show 

how it produces paralysis. 

14. Discuss fits ; their causes, forms, and treatment. 

15. Discuss panics. 



CHAPTER XXXIII 

EFFECTS OF NARCOTICS UPON THE MIND 

572. Stages of action. — A perfect engine acts smoothly, 
and with an ease of motion which suggests a delight in its 
work. The body is an engine at the service of the will. 
A derangement of any part disturbs the action of the 
brain according to the extent of the disorder. While little 
or no alcohol can ever be found in the brain, yet the leu- 
comaines and other poisons produced by the action of 
alcohol reach the whole body, and produce a profound 
effect upon the brain sooner than upon any other part. 
Three stages of the effects of alcohol are well marked : — 

First, there is a stage of stimulation ; second, the cells 
act in an uncertain manner. This is the stage of disturbed 
action ; third, the cells act slowly or even cease to act. 
This is the stage of paralysis. All three stages are often 
seen in drunken men upon the streets. 

573. Stage of stimulation. — A small amount of alcohol 
causes the blood to circulate more rapidly. More food 
reaches the brain cells, and so they show more activity. 
It produces a happy state of mind in which men over- 
estimate their abilities. Men drink mainly for this effect 
of the alcohol. 

Some gifted men with weak wills exert themselves only when under 
the influence of strong drink, and from this fact many reason that 
alcohol increases the brain power. These gifted men hang about the 
saloons, eating little and drinking much. In this condition their brains 
receive no strength or energy to devote to any object. A drink fur- 

315 



3l6 APPLIED PHYSIOLOGY 

nishes a quick stimulation which at once excites the brain to great 
activity. Thus it is enabled to do brilliant work while the effects of 
the alcohol last. In half an hour the poisonous effects assert them- 
selves, and the man's condition is worse than ever. Good food and a 
regular life would give such a man a continuous store of energy with 
which he could perform brilliant work day after day. Alcohol is such a 
poor substitute for the food that it enables him to work only for a few 
moments at a time. 

574. Stage of disturbed action. — The stimulation of a 
drink of alcohol is uncertain, and, at best, lasts only for a 
few minutes. Alcohol uses oxygen which would otherwise 
be available for the brain cells as well as for the other 
cells of the body. An ounce and a half of alcohol a day 
will begin to interfere with oxidation and to disturb the 
brain, and far less will do so if it all is taken at once. 

575. Moral effect. — Alcohol weakens and disturbs the 
action of the brain cells, beginning with those most 
highly developed. These are thoughts of our relation to 
other men. So a person beginning to be under the influ- 
ence of drink will be selfish and inconsiderate of others. 
He will insult his friends and get angry without cause. 

576. Effect upon his judgment. — The judgment or 
reasoning concerning the effect of one's acts upon himself 
is the next to be disturbed. He becomes daring and 
careless. He proposes impossible plans in business. If 
he has a tendency to commit a crime, he will do it now. 
Many a thief or murderer has gotten himself into this 
state of drunkenness to enable him to commit his crime 
recklessly. If a man has a tendency to swear or to be 
unkind, he will show it, for the restraint of judgment is 
gone. The blunted judgment takes no note of coming 
danger or of business failure. Many a man drinks to 
drown trouble. 



EFFECTS OF NARCOTICS UPON THE MIND 317 

577. Effect upon the motor regions. — Shortly after the 
judgment is clouded the motor regions begin to fail. Then 
the hand will be unsteady, and the legs will totter as they 
support the body. The person is now visibly drunk, and 
his judgment is so far gone that he could not decide where 
to go even if his legs could carry him. The cerebellum is 
also affected, so that he is still more uncertain in his 
movements. 

578. Effect upon the sensory regions. — Next after the 
motor regions, the sensory regions begin to fail. Sensa- 
tions of touch are first affected, so that the drinker cannot 
feel the glass at his lips. In former days it used to be 
the custom to make a person drunk and insensitive before 
he underwent a surgical operation. After the sensations 
of touch are benumbed the sight begins to fail. A 
drunken man sees double, or the buildings and trees seem 
to sway and dance before his eyes. Hearing, smell, and 
taste are also lessened, so that he does not heed loathsome 
surroundings, but will lie contented in a filthy gutter. 

579. Stage of paralysis. — When the thought, motor, 
and sensory regions of a man's brain are all weakened or 
stopped in their action, the mind is dull and drowsy, and 
soon he is in a condition resembling a deep sleep, from 
which he can be roused only with difficulty. The medulla 
and spinal cord still carry on the processes of life, but 
they too begin to be overpowered. By the time the 
cerebrum is almost overcome, the spinal cord is also much 
decreased in action so that there is no response to pricks 
or blows. Then the medulla is all that remains of the 
central nervous system. It continues to send out impulses 
for respiration. The respiration and circulation are the 
only remaining signs of life, but even they are weak, 
and may become almost imperceptible. Since little oxy- 



3l8 APPLIED PHYSIOLOGY 

gen enters the body, little heat is produced. If the night 
is at all cold, the drunken man is in great danger of 
freezing to death. It is only a step to the total cessation 
of the action of the medulla and failure of respiration. 

In cities men often are found in the streets in the last 
stage of drunkenness. They closely resemble cases in 
which the action of the brain is destroyed by a severe 
blow upon the head which leaves no external mark. 

580. Effects of long-continued drinking. — Either heavy 
or moderate drinking may cause in the brain and mind 
a slow change which resembles an excessively slowly 
developed drunken state. As in drunkenness, the first 
change is a disregard for the comfort of others. Then 
the thoughts wander, and the mind cannot grasp a situa- 
tion as it once could. Later the motor region is affected so 
that the hand trembles and the gait is unsteady. All these 
changes are like those which naturally occur in old persons. 
Drink makes a person old too soon. In many drinkers the 
judgment entirely disappears, and the drinker is insane. 
He is in a continual state resembling drunkenness. Alco- 
hol produces more insanity than all other causes combined. 

581. Effects of bad company. — The low companionship which 
a drunkard keeps, itself tends to dwarf the mind and to make one care- 
less in morals and judgment. Men also lead each other into tempta- 
tion. If a man were alone, one drink might satisfy him, but meeting 
others, he lingers to talk, and so drinks again to keep company with 
the rest. 

582. Delirium tremens. — After a prolonged drunken state, or 
after severe injury, a heavy drinker is liable to violent disturbance of 
the mind, called delh'hun tremens. In it his sensory regions form 
exaggerated memories of fantastic and hideous views, in which demons 
and foul reptiles seem present on purpose to torment him. In his fear 
he will cry out and will use violence in his endeavors to escape. The 
trouble may last continually for several days, and may permit the suf- 
ferer to take neither food nor sleep. 



EFFECTS OF NARCOTICS UPON THE MIND 319 

583. Alcoholic inheritance. — The weak body and mind of a 
continued drunkard are almost surely transmitted to his children, but any 
one who drinks at all may transmit some undesirable traits. The appe- 
tite for liquor also may be transmitted to the children. If they are kept 
from temptation, they will lead temperate lives, but they will be very apt 
to yield to the desire for drink if the temptation is throwm in their way. 

584. Treatment of the alcoholic habit. — By a few repeti- 
tions of drink the meinory of its sensations becomes so 
strong that it overrules the thoughts and will, and compels 
its own gratification in more drink. At first, a man can 
resist the appeals of his appetite, but after the cells of the 
sensory region have gained gratification a few times, they, 
instead of the will, direct the motor region to secure the 
drink. Many a drunkard can no more control his appetite 
than he can control the memory of the drink. What was 
once a pleasant memory of the subordinate sensory region, 
becomes the giant demon, enslaving the kingly thought 
regions. 

A drinker should not be laughed at or scorned, but he 
should be encouraged to use his will in overcoming the 
desire for drink. To this end everything ennobling should 
be placed in his way. Good books, good companionship, 
and, above all, the encouragement of sincerely Christian 
people are almost absolute necessities in his reformation. 

Drugs have almost no effect upon the habit, for they 
cannot abolish memory nor increase the will power. Total 
abstinence, not only from the drink, but also from buildings 
where it is sold and from the association of those who 
have been drinkers, is necessary for a cure. 

585. Tobacco. — By smoking, a greater amount of blood 
is drawn into the head, and the increased flow of blood 
seems to make the brain more active. Sucking air through 
a small quill produces the same effect upon the brain as 



320 APPLIED PHYSIOLOGY 

sucking smoke through a pipe. In fact, smokers often 
cannot tell by the taste alone, whether the pipe or cigar is 
alight or not ; but they unconsciously judge mainly by see- 
ing the smoke. Since tobacco weakens the heart, less 
blood will flow through the body when tobacco in any 
form is used, and this fact will tend to make the mind act 
less strongly than before. The nicotine is also a direct 
nerve poison. 

586. Drug habits. ^~ Opium, cocaine, and other narcotic 
drugs whose use may become a habit, affect the mind in 
the same way as alcohol. Every one who habitually uses 
any of these drugs will surely become a mental as well as 
a physical wreck. Opium, especially, seems to have a 
fiendish effect in destroying the morality of its users. 
They begin by lying and cheating in order to obtain the 
drug without the knowledge of their friends, and they 
finally end by becoming dishonest in all things. But the 
drug produces a weak mind and body which soon end in 
death. Most of these drugs are far more dangerous than 
tobacco or alcohol. 

587. Ether and chloroform anaesthesia. — Ether and chloro- 
form are both substances manufactured from alcohol. When they are 
breathed into the lungs they produce effects which resemble a rapid 
state of drunkenness carried to its last stage. For a brief time, the 
brain is excited and then its faculties disappear one after another. In 
from five to fifteen minutes the brain and spinal cord are completely 
overcome, and only the medulla continues in action to carry on respira- 
tion and the circulation of blood. A person may be safely kept in this 
condition for two or three hours. Upon stopping the inhalation the 
effects pass off in reverse order, until in from ten minutes to an hour 
one has the full use of his brain again. The thought regions are over- 
come long before the motor regions, and so a person taking ether may 
struggle and cry out in apparent agony long after he has become com- 
pletely unconscious. The struggling is reflex and takes place while a 
person is insensible to suffering. 



EFFECTS OF NARCOTICS UPON THE MIND 321 

SUMMARY 

1. Because a small quantity of alcohol stimulates the 

heart and increases the flow of blood in the brain, 
it stimulates the mind to greater action. This lasts 
for a short time only. 

2. A little more alcohol is a narcotic to the brain cells 

and weakens them so that they act in an uncertain 
manner. 

3. The first action to be disturbed is one's thoughts of 

the welfare of others, and the second is the judg- 
ment of one's own affairs. At this stage the actions 
are wild and foolish. 

4. Next the motor region is disturbed, and a man is now 

noticeably drunk. 

5. Next his sensory regions are disturbed so that he can- 

not see and hear and feel so well as he should. He 
is now dull and sleepy, or dead drunk. 

6. Next the medulla is affected so that the respiration 

and action of the heart are disturbed. Then death 
is near at hand. 

7. Continued drinking slowly overcomes the faculties of 

the mind in the same order that they are overcome 
in drunkenness. When the cells are seriously 
affected, the person is insane. 

8. The habit of taking alcohol may become so deeply 

set in the brain cells that it is a disease overcoming 
the will. 

9. Sucking in tobacco smoke causes more blood to flow 

to the brain, and so slightly increases its power, but 
the tobacco itself weakens the brain. 
[O. Opium, cocaine, and all other drugs, when habitually 
used, always weaken and destroy the mind, 
ov. PHYSIOL. — 21 



322 APPLIED PHYSIOLOGY 



REVIEW TOPICS 

1. Tell why alcohol affects- the brain and give the three 

stages of its effects. 

2. Describe the stage of stimulation. 

3. Trace the career of a man as he becomes more and 

more under the influence of drink, giving the effects 
of alcohol upon the moral feelings ; upon the judg- 
ment ; upon the motor region and cerebellum ; upon 
the sensory region ; and upon the medulla. 

4. Describe the permanent effects which long-continued 

drinking produces in the brain. 

5. Show how the bad company kept by drinkers affects 

their minds. 

6. Describe delirium tremens. 

7. Show that the taste for alcohol and the effects of its 

use may be transmitted to children. 

8. Show that the alcohol habit is a disease, and give its 

treatment. 

9. Tell how tobacco affects the brain. 

10. Tell how drug habits, as opium using, affect the 

brain. 

11. Tell how ether and chloroform produce insensibility, 

and how the state resembles drunkenness. 



CHAPTER XXXIV 

TASTE, SMELL, AND HEARING 

588. Touch. — Touch is a special sense. Its sensations 
are aroused without the need of any special organ. So 
the discussion of sensory nerves is really a discussion of 
the special sense of touch. (See p. 269.) 

589. Taste. — Taste is a special sense which is located 
in the tongue, palate, and pharynx. All these parts are 
endowed with a delicate sense of touch, but in addition 
two pairs of cranial nerves carry special sensations of taste. 
The impulses are aroused by the direct action of sub- 
stances upon the nerves. The motions of chewing and a 
good flow of saliva aid the sense of taste by bringing food 
in contact with the nerves, while a dry substance, or one 
which will not dissolve in water, can have no taste. All 
tastes are some combination of sweet, sour, bitter, and salt 
tastes. Sweetness and sourness are recognized mainly by 
the front part of the tongue, and bitterness and saltness 
by the back parts and pharynx. 

Taste is greatly influenced by the sense of smell. The 
real taste of coffee is greatly changed by the odor which 
reaches the back part of the nose as it is swallowed. 

590. Use of taste. — Taste enables a man to detect 
spoiled or unwholesome food. The sense is capable of 
great education. The prices of different grades of tea are 
determined by expert tea tasters, who devote their whole 
time to tasting different samples. Alcohol and tobacco 

323 



324 



APPLIED PHYSIOLOGY 



irritate the nerves in the mouth and so bkmt the taste for 
good food. For this reason a drinker does not enjoy plain 
food, but requires spices to excite his taste. 

591. The nose. — Impressions of smell originate within 
the nose. Each nostril leads to a wedge-shaped cavity, 




The outer wall of the nose. 



a the nerve of smell at the base of the 

brain. 
b air spaces in the skull bones. 
c branches of the nerve of smell. 



d curved curtains of bone. 

e opening of the Eustachian tube. 

f soft palate. 

g upper jawbone. 



which opens into the pharynx. The inner wall of each 
cavity is smooth, and is formed by the thin bone that 
separates the two nostrils. Each outer wall is formed by 
three very thin bones which hang down like narrow cur- 
tains. They nearly cover cavities, called sinuses, which 
are situated in the neighboring bones. One sinus occupies 
the interior of the upper jawbone, and is called the antrum. 
The part of the skull behind the eyebrows is honeycombed 
with small cavities, called the frontal sinuses. 



TASTE, SMELL, AND HEARING 325 

592. Olfactory nerves. — From the under surface of the 
brain, about twenty nerves extend through perforations in 
the upper part of the nose and spread out over the upper 
one third of the surface of the nasal cavities. An odorous 
gas entering the nose comes in contact with the ends of 
these nerves and excites the sense of smell. An odor is 
found only in substances which can be turned to a vapor. 

The olfactory nerves are so delicate that they can perceive the 
presence of gases which cannot be detected in any other way. Some 
substances excite the sense of smell when they are in such small quan- 
tities that they are given off for years without causing a perceptible 
lessening of the weight of the substance. 

When too much mucus covers the nerve endings, or when the sur- 
face of epithelium is dry, no gas can reach the nerves, and then the 
sense of smell is diminished. A cold in the head can produce either 
condition. 

593. Use of smell. — Smell is a warning against foul air 
and decaying matter. The gases themselves are in too 
small quantities to do harm, yet they are a sign that 
other substances are present which can harm the body. 
Air which has no odor is almost surely fit to be breathed. 
Meat which has a pleasant odor is almost certainly fresh. 

Tobacco smoke and snuff are irritating to the delicate 
nerves of smell, and partly deprive its users of nature's 
most useful protection against foul air. 

594. The inner ear. — Sound is produced by certain air 
waves which are received by nerves in the ear. There 
they excite impulses which the brain interprets as sound. 
In the hard bone, which rises from the bottom of the 
skull by each ear, is a tortuous cavity, called the laby- 
rinth or internal ear. The center of the labyrinth is about 
one eighth of an inch in diameter, and is called the ves- 
tibule. From the vestibule there extends a small spiral 



326 



APPLIED PHYSIOLOGY 



tunnel, called the cochlea^ which is like the inside of a 
snail's shell, and also three other tunnels called the semi- 
ci7Xiilar canals, from their shape. 

The labyrinth is filled with a clear liquid, and is lined 
with epithelial cells, among which the nerves of hearing 
end. Upon the surface of the epithelium are cilia, among 
which are fine hard particles called the ear sand. The air 
waves produce waves in the liquid which beat against the 




, Diagram of the ear. 

a outer air passage. / semicircular canals. 

b membrana tympani. g vestibule of inner ear. 

c malleus or hammer bone. h cochlea, 

d incus or anvil bone. i Eustachian tube, 

e stapes or stirrup bone. / tympanum or middle ear. 

cilia and produce the sense of sound. Waves in the fluid 
surrounding the nerves must occur at least sixteen times a 
second in order to produce a sound. When they occur 
more than thirty-eight thousand times a second, they are 
too rapid for the nerves to take account of their motion, 
and so no sound at all will be heard. 

The semicircular canals do not seem to be essential to hearing, but 
when they are diseased a person is unable to balance himself so as to 
walk or even to stand. The movements of the fluid in the canal seem 
to produce nervous impressions which, in the cerebellum, excite such 
reflex actions as are necessary to balance the body in an upright position. 



TASTE, SMELL, AND HEARING 327 

595. The middle ear. — To make hearing distinct, a 
special mechanism is provided for transmitting the air 
vibrations to the inner ear through two outer cavities. 

A small aperture connects the inner ear with a middle 
cavity called the middle ear, or tyinpamim. The middle 
ear is half an inch long and a quarter of an inch broad. 
It is lined with mucous membrane and is filled with air. Its 
outer end is closed like a drum, by a thin leaf called the 
druvi membrane or membrana tympanic while a similar mem- 
brane closes the aperture to the inner ear. The cavity of 
the middle ear is greatly increased by its extending back- 
ward into a bony projection called the mastoid process, 
which can be felt just behind the outer ear. It connects 
with the pharynx by means of a tube which is about the 
size of a knitting needle and is called the Eustachian 
tube. The act of swallowing opens the tube. 

596. Bones of the middle ear. — The essential part of the 
middle ear is a chain of small bones called the malleus^ 
incus, and stapes, which extend across its cavity from one 
membrane to the other. 

Air waves, striking the ear drum, throw it into vibra- 
tions, which the chain of bones transmits to the inner ear. 
The tympanum and its extension into the mastoid cells 
act like the sounding box of a violin to increase the 
vibrations. 

597. Deafness. — The Eustachian tube permits air to pass in and 
out of the middle ear so as to keep the air pressure within the same as 
it is outside. When it is closed, the air pressure outside may change, 
and thus the drum membrane will be pressed upon and prevented from 
vibrating freely. This results in partial deafness. Enlarged tonsils 
and adenoid vegetations are liable to cause a stoppage of the tube and 
to produce deafness, and for this reason they should always be removed. 
WJien the tube is stopped, there is a feeling of fullness in the ear, and 
roaring or singing noises will be heard. 



328 APPLIED PHYSIOLOGY 

Deafness due to a stoppage of the Eustachian tube is the most com- 
mon form. It often can be relieved by opening the tube by swallow- 
ing. By blowing the nose hard with the nose and mouth closed and at 
the same time puffing out the cheeks and swallowing, one can almost 
always force air through the tube into the ear and thus relieve the deaf- 
ness. This should be done several times a day. 

Sometimes an inflammation extends from the pharynx up the Eusta- 
chian tube and sets up an inflammation in the middle ear like that in 
the throat. Mucus and matter then collect in the middle ear and 
press upon the ear drum, causing a severe earache. If the tube does 
not open, the membrane may burst and allow the matter to run out of 
the ear. 

598. A running ear should be kept clean by cleansing it with warm 
boiled water as often as the matter collects. Sometimes in running ears, 
the disease eats away the bones and produces inflammation of the brain. 
For this reason running ears are always dangerous. 

Some drugs may produce a ringing in the ears and partial deafness. 
Quinine, which is taken for malaria, and salicylic acid, which is taken for 
rheumatism, may cause it, but the eflfects pass off" within a few hours. 

Boxing the ears suddenly compresses air against the drum mem- 
brane, producing pain and sometimes even bursting the membrane. 
Loud reports, as of cannon, cause such extensive and painful vibra- 
tions of the membrane that deafness may result. 

599. Early in life a child may become deaf, and yet no 
one may be aware of the trouble. Then the child is appar- 
ently inattentive and does not answer when spoken to. 
At school the teacher may ascribe his lack of attention to 
carelessness or ill temper. In consequence, the child re- 
ceives unjust punishment. The hearing of every dull and 
inattentive child should be examined. 

600. The outer ear. — Outside of the drum membrane 
is a passage to the air about an inch in length and one 
quarter of an inch in diameter, formed partly of bone and 
partly of flesh. Around its opening is a shell-shaped fold 
of fiesh which, together with the passage, is called the 
outer ear. Connected with it are rudimentary muscles 



TASTE, SMELL, AND HEARING 329 

which are so well developed in some persons that they can 
move their ears as a horse does. 

601. Ear wax. — The epithelium of the outer half of the 
passage secretes a kind of bitter and sticky wax which 
keeps insects and dust from reaching the drum mem- 
brane. The epithelium grows outward towards the surface 
like the nails, and carries the wax with it, thus preventing 
its accumulation. Often in picking the ears the wax is 
pushed against the drum membrane so that it cannot 
vibrate. Next to throat trouble this is the most common 
cause of deafness. The accumulated wax can be softened 
and removed by gently syringing with warm water. Wax 
can best be removed with the loop of the smallest-sized 
hair pin, taking care not to insert it far enough to touch 
the drum membrane. 

602. Illusions of hearing. — Too dense or too rare air in 
the middle ear, too much blood circulating in the inner ear, 
the use of certain drugs, as quinine, blows upon the head 
or wax in the ear, are all causes which may excite the 
nerves of hearing. Then the impression goes to the 
brain as though a real sound had excited the nerves. 

The cells of the brain itself may interpret a sensation 
wrongly ; thus an insane person may think that the sound 
of his own pulse beating in his ears is the echo of the 
blows of demons within his head. 

Sometimes persons recall memories of sounds so vividly 
that they seem to be real. This occurs naturally in dreams, 
but it may occur in an insane person at any time. 

603. The ear in lower animals. — In four-footed animals 
and in birds the ear is the same as in man. In turtles and 
frogs there is no outer ear, but the drumhead lies just 
under the skin, forming a visible circle behind the eyes, 
while the middle ear contains a single bone. In the snake 



330 APPLIED PHYSIOLOGY 

there is no external or middle ear, although a bone extends 
from the inner ear to a kind of drum membrane just under 
the skin. In the fish there is no external or middle ear, 
and the labyrinth has no cochlea, but the vibrations are 
transmitted only through the skull. In the lobster there is 
a small cavity filled with liquid, in which are the endings 
of the nerves of hearing. The vibrations producing sound 
are transmitted to the bag through the sides of its head. 
Thus all animals which have ears at all, possess what in 
man is the internal ear. 



SUMMAR"X* 

1. The sense of taste is excited by substances which 

become dissolved in the saliva and excite special 
nerves in the tongue and pharynx. 

2. The sense of taste enables one to distinguish good 

food from bad. 

3. The sense of smell is excited by minute amounts of 

gas, which excite special nerves in the upper part 
of the nose. 

4. Smell guards us against foul air and decayed sub- 

stances. 

5. Sound is produced by vibrations of the air. 

6. The inner ear consists of winding canals filled with 

liquid into which special nerves project. Vibra- 
tions of the air excite the nerves and produce the 
sense of sound. 

7. The middle ear consists of a bony cavity across which 

three small bones convey the vibrations of the air 
to the inner ear. 

8. Deafness is often caused by the Eustachian tube being 

stopped. 



TASTE, SMELL, AND HEARING 33 1 

9. Inflammation of the throat may extend mto the middle 
ear and produce an earache. 

10. Enlarged tonsils and adenoid vegetations are the two 

principal causes of earache and deafness. 

11. Running ears should be kept clean. 

12. In all animals having a hearing apparatus, the essen- 

tial and often the only part is the inner ear. 

DEMONSTRATIONS 

130. Examine the tongue of one of the pupils. Notice that its sur- 
face contains three kinds of projections. There is a V-shaped row of 
large, flat, and smooth projections upon its back part. There are red 
pinhead-sized projections scattered over the whole front surface. There 
are also fine projections like velvet spread over the whole surface. In 
all these projections the nerves of taste seem to end. Examine also a 
cat's tongue, and note the stiff hairs upon its surface. 

131. Test the power of taste in different parts of the tongue. Place 
a bit of a sweet or of a sour substance in the back of the mouth, and notice 
the slight taste, while it is easily tasted in the front part. Now place 
some salt or bitter substance upon the front of the tongue. Notice that 
it has little taste until it spreads to the back part. 

132. Saw lengthwise through a calf's head so as to open the nose. 
Notice the smooth inner surfaces of the nostrils, and their furrowed 
outer surfaces produced by the folded bones. Notice that the nostrils 
open into the pharynx. (See demonstration 35.) 

133. Have a butcher remove the bone containing the middle and 
internal ear from a calf's skull. Carefully cut away the shell of bone 
over the middle ear. One can judge of its position by measuring down 
the outer air passage. Notice the size and shape of the middle ear. 
Notice the ear drum, anH the three little bones which stretch from it 
entirely across the cavity. Notice also that the last bone fits into the 
small opening leading into the inner ear. 

134. The inner ear will be more difficult to show, for it is small and 
complicated, and is situated deep in a very hard bone. Cut away the 
bone a little farther in, when the cochlea may be opened, and possibly 
a semicircular canal will be recognized. The spiral tube of the cochlea 
is barely ' of an inch in diameter, while the semicircular canals are as 
small as a sewing needle, but yet form loops about I of an inch across. 



332 APPLIED PHYSIOLOGY 

REVIEW TOPICS 

1. Describe the process of tasting, and tell how smell 

influences the sense of taste. 

2. Give the use of the sense of taste. 

3. Describe the endings of the nerves of smell in the 

nose, and tell how the sensation of smell is pro- 
duced. 

4. Give the use of the sense of smell. 

5. Describe the inner ear : its cochlea, semicircular 

canals, and nerves of hearing, and tell how they act. 

6. Describe the middle ear : its bones, the two mem- 

branes which close it, and its Eustachian tube. 

7. Show how a stoppage of the Eustachian tube may 

lead to deafness ; to running ears. 

8. Show how throat trouble may cause ear disease. 

9. Tell how to care for running ears. 

10. Show why boxing the ears is dangerous. 

11. Describe the outer ear: its air passage and wax. 

12. Show how the ears may seem to hear sounds which 

do not exist. 

13. Describe the ear in a frog ; in a snake ; in a fish ; in a 

- lobster. 



CHAPTER XXXV 



THE EYE 



604. Light. — Straight Hnes of Hght called rays pass off 
from objects m all directions. Each ray is supposed to be 



a vibrating 
substance 
which fills 



line in a thin 
called ether, 
all space. 




The vibrations of ether take 
place many milHons of times 
each second. In sound the air 
vibrates only a few hundred 
times. Light travels nearly 
185,000 miles each second, while 
sound travels about 1000 feet in 
the same time. Light waves are 
from 70 500 to ^0700 inch in 
length, but each sound wave 
reaches several feet. The length 
of a wave of light determines its 
color. Red waves are about 
twice as long as violet waves. 
A mixture of all colors produces 
white light, while black is due 
to the absence of light. Colors 
which, hke red and green, form white light, are called complementary 
colors. 

In passing through glass or other clear substances, rays of light may 
be bent from their courses. By a properly shaped glass called a lejis, 
rays may be spread apart or may be brought together in a point called 

333 



Diagram of light passing from an object. 

It passes in every direction, and, falling 
upon a screen, produces a confused multi- 
tude of images, which form only a mass of 
light, but no one clear image. 



334 



APrUED PHYSIOLOGY 




Diagram of the formation of an image with a 
lens. 

a an object sending off light. 

b a lens which brings all the rays from any point 

in the object together again into a single 

point. 
c image of the object (2. 



2. focus. If the focus falls upon a screen, an image of the object giving 

the light will appear. By changing the kind and the position of the 

lens the image may be 
made either larger or 
smaller than the real 
object. 

Light has the power to 
produce a chemical change 
in substances. Photog- 
raphy and bleaching 
clothes are examples of 
the action of light. In 
photography a prepared 
plate is inclosed in a tight 
black box, into which light 
from an object is admitted 
through a small lens. 

The lens brings the light to a focus and forms an image upon the 

plate. 

605. The eye. — The eye is an apparatus like a photog- 
rapher's camera, but is more perfect. It consists of a 
round, hollow shell about |^ of an inch in diameter, formed 
of a very tough membrane about -^ of an inch in thick- 
ness, called the sclerotic coat. The sclerotic coat is lined 
with a thin black membrane called the cJioroid coat, which 
carries the blood tubes, and is colored black so as to 
prevent reflection of the rays of light. Inside of the 
choroid coat is a very thin and transparent membrane 
called the retina. The cavity of the eyeball is filled 
in front with a thin, clear liquid called the aqiieoti-s humor, 
while its back part contains a thick, jellylike fluid called 
the vitreous humor. The two humors keep the eyeball 
distended and in shape. 

The nerve of sight, called the optic nerve, enters the 
back part of the eye and separates into fine threads which 
end in microscopic rods set closely together on their ends 



THE EYE 



335 



in the retina. The retina corresponds to the photographic 
plate of a camera. A bulging transparent tissue, called 
the cornea, forms a round window through the front part 
of the eyeball, and admits light to the retina. Behind the 
cornea is hung a curtain called the iris, in whose center is 
a hole called the pupil. The iris is colored to a shade 






The human eye. 




a bone of the orbit. 


e retina. 


i cornea. 


b muscle which moves 


/ eyelid. 


j muscle which changes 


the eyeball. 


g ins. 


the shape of the 


c sclerotic coat. 


h lens. 


lens. 


d choroid coat. 




k optic nerve. 



varying from blue to dark brown, and it is this which gives 
the color to the eye. 

The iris is composed of muscle fibers which can contract so as to 
make the pupil smaller. A strong light acts in a reflex way to cause 
the iris to contract and make the opening of the pupil smaller, but in a 
dim light the pupil is large, so as to admit all the light possible. Thus 
the iris regulates the amount of light admitted to the retina. 

606. Sight. — Behind the pupil is a lens whose shape 
can be changed at will by the action of muscles. The 



336 APPLIED PHYSIOLOGY 

lens brings the light to a focus so as to form an image of 
an object upon the retina. In the cells of the retina are 
particles of brown coloring matter in which light produces 
an instant change. This excites in the optic nerve an 
impulse which the brain interprets as sight. 

607. Coverings of the eye. — The eyeball is loosely situ- 
ated in a deep depression of the skull, called the orbit. 
The space between it and the bone is padded with fat and 
crossed by numerous muscles, nerves, and blood tubes. 
Thus it is thoroughly protected from injury. It can be 
freely turned at will in all directions by six slender mus- 
cles which rise from the back part of the orbit. It is pro- 
tected in front by two thin but strong lids, which can be 
moved up and down at will. From the edges of the lids 
there project two or three rows of stiff curved hairs, which 
still further protect the eye. The lids can be closed by a 
flat circular muscle which completely surrounds them. 
The insides of the lids and the front side of the eyeball, 
except the cornea, are covered with a soft mucous mem- 
brane, called the conjunctiva. 

608. Tears. — The conjunctiva and cornea are mois- 
tened by a saltish fluid called tears. Tears are secreted by 
a gland called the lachrymal gland, which is situated just 
above and to the outer side of the eyeball. At the inner 
end of the edge of each lid is the opening of a small tube 
which unites with the tube from the other lid and forms a 
single tube called the nasal dnct, leading to the nose. 
Ordinarily the nasal duct drains away the tears as fast 
as they are formed, and sometimes, as in crying, their 
salt taste can be noticed in the mouth. Often they are 
produced so fast that some run over the lids and fall down 
the face. The uses of tears are to wash away particles of 
dust which fall upon the eyeball, and to moisten its surface. 



THE EYE 337 

609. Field of view. — A person can clearly recognize 
objects in only a small part of the field of view just in 
front of the eyes, while the rest seems to be only indistinct 
shadows. To be distinct, the image must fall upon the 
part of the retina less than ^ of an inch across, which is . 
situated directly behind the cornea. In reading a book, 
the eye can distinctly see two or three words at once, but 
by rapid and unconscious movements of the eyes sidewise, 
we cover a larger field of view. 

610. Duration of sensations. — The sensation of sight is 
produced almost instantly when the eyes are directed 
towards an object, but the image persists for -^-^ of a 
second. If a succession of pictures of a moving object 
are thrown upon a screen at that rate, the object will seem 
to go through its motions without interruption. Birds 
flying and waves dashing upon the beach may be thus 
shown absolutely true to life. A point of light swung 
about a circle seems to be a shining ring. If two colors 
are revolved at that rate, the eye no longer sees either one, 
but a mixture of the two. Thus a blue and a yellow spot 
side by side, when revolved before the eye, seem a single 
green spot. 

611. Color blindness. — Sometimes the nerves of the 
retina are unable to recognize certain colors. In the 
most usual form of color blindness red is supposed to 
be green or gray. In locomotive engineers and sailors 
color blindness may be a serious defect, for they are 
guided by different colored signals, especially those con- 
taining red. 

612. Exhaustion of the retina. — When the eyes look 
steadily at objects for a long time the vision becomes 
blurred. If one gazes steadily at a bright colored object, 
the retina is fatigued by that color. A white object looked 

OV. PH\'SlOL. — 22 



338 APPLIED PHYSIOLOGY 

at now will show a colored spot shaped Hke the first object, 
for a part of the retina is no longer able to recognize all 
the colors which make white light. Its color will always 
be complementary to the color of the object first looked at. 
Thus when a red object is used first, a green image ap- 
pears. The eye is really made color blind for a brief 
period. 

Ordinary lamps and gas jets give a yellowish light, while the sunlight 
is white. So by lamp light, the colors of objects seem to be changed. 
In incandescent electric lamps the light is given off from a white-hot 
filament. Owing to its steadiness, its color and the absence of heat 
and foul gases, it is the most agreeable light in common use. 

613. Care of the eyes. — No light should be strong enough to 
dazzle the eyes. When, as in public halls, bright lights are in front of 
the eyes, there is a natural tendency to gaze directly at them, thereby 
tiring the retina. It would be better to look at the darkest objects in 
the room. 

It is best to have the light come from behind the eye. In working 
with a lamp in front of the eyes, a shade should cover either the light 
or the eyes. When the sun shines brightly upon the snow the excess 
of light exhausts the retina. Then the eyes become painful, and blind- 
ness may result. 

614. Contraction of the pupil. — A strong light excites 
the reflex center in the optic tubercles to send out an 
order for the contraction of the muscles of the iris so as 
to make the pupil smaller. On the other hand, in the 
dark the pupil is large, so as to admit all the light possi- 
ble. When a light is very strong, the reflex centers send 
orders to the muscles both of the upper and lower lids, 
and of the eyebrows to pucker themselves over the eyes, 
so as to leave only a narrow slit for the entrance of light. 
In this way the eyes are well protected against too strong 
lights, but the contracted muscles may become tired and 
painful. 



THE EYE 339 

615. Accommodation. — Rays of light coming from a dis- 
tant object are less diverging than when coming from one 
near by ; then the lens does not need to bend them so much 
as in seeing objects near by. Adjusting the lens of the 
eye to near or far vision is called accoiyiniodation. When 
the eye muscles are at perfect rest, the eye is accommo- 
dated to see clearly at all distances over twenty feet. So 
distant vision requires no effort. When one wishes to see 
an object less than twenty feet away from the eye, the 
muscles must cause the lens to become more curved. 
Thus the eye can see clearly up to about five inches from 
the eye. Vision is best when the object is about ten 
inches from the eye. 



/)^--ri: 



Diagram of the eye in far sight. 

The lens b does not bring the rays from a point of light a together soon enough. 
So the rays fall over the whole surface of the retina from d to e, making a confused 
image instead of a clear point. When the rays spread less apart, as when the light 
is moved farther away, to/ the lens brings them together sooner. Then the rays 
fall upon a single point of the retina at^, and thus form a clear image. 

616. Far sight. — At the age of about forty-five, the muscles of 
the lens lose some of their power of contraction and are unable to 
make the lens so curved as in youth. Then the eye cannot be adjusted 
for near vision, while for far vision the sight is as good as ever. So an 
old man holds his newspaper at arms' length. He also aids the action 
of his lens by placing before his eye a spectacle lens which corrects 
the deficiency in the lens of his eye. 

617. Near sight. — in young people the lens often brings the 
rays together too soon. 7 lie rays must be made more diverging by 




340 APPLIED PHYSIOLOGY 

bringing the object very near the eye. Such persons cannot see dis- 
tinctly at a distance greater than a few inches, but walk about as in 
a perpetual fog. 




Diagram of the eye in near sight. 

The lens h brings the rays from a point of light a together at c too soon. So 
the rays cross and fall over the whole surface of the retina from d to e, making a 
confused image instead of a clear point. When the rays are spread apart by 
bringing the light near the eye, as at f, they come together farther away upon the 
other side of the lens, as at g. Thus they fall upon a single point of the retina 
and produce a clear image. 

Near sight can be remedied by placing in front of the eye a lens 
which will make the rays more diverging. So the spectacles have the 
glasses hollowed out instead of bulging. 

618. Astigmatism and headaches. — Sometimes the lens or 
cornea is more curved in one direction than in another. Then a part 
of the object will seem distinct, and another part blurred, and the eye 
muscles will constantly change the focus in the attempt to obtain a full 
and clear image. This is very tiresome to the eyes, and often causes 
severe headaches. The remedy is to use a glass which is curved in one 
direction only, so as to correct only the defective part of the lens. 

619. Cataract. — Sometimes the lens becomes hard and white. 
Then no light can pass through, and there is total blindness. This is 
called a cataract. By a simple and safe operation the lens can be 
removed, when the light will fall upon the retina as before. Spectacles 
to take the place of the lens enable the person to see. 

620. Judgment of position. — In perfect vision each eye 
is turned toward the same point, so that the irriages fall 
upon corresponding points of the retina. But the two eyes 
view an object from different positions, and so the images 



THE EYE 341 

are not exactly alike. The blending of the images will 
give the idea of solidity or of position in distinction from 
the impression that everything is a flat surface. This per- 
ception is not natural, but must be learned. Distant objects 
always seem flat. 

621. Movements of the eyes. — If the images of an object do 
not fall upon corresponding parts of the retinas of the two eyes, two 
images will be seen. Sometimes a muscle will draw one eye aside so 
that it does not look in the same direction as the other eye. A person 
with this defect is said to be cross-eyed. 

Young babies have no control of their eye muscles, and so have no 
distinct vision, except as they catch accidental glimpses. A bright 
cloth gives them a sensation of color at whatever distance it is held, 
and so amuses them. At about the age of three months they begin to 
gain control of their muscles, so that they can focus the eyes and turn 
them to any object at will. It takes them several months more to 
acquire a knowledge of solidity and position. 

Anything touching the eye causes the lids to close in a reflex man- 
ner for protection. Tears flowing over the eye cause the lids to wink 
and distribute the moisture over the whole surface. 

In reading in the cars, the constant jarring of the paper compels the 
muscles of the eyes to be in constant action to adjust the eye to the 
ever-varying positions and distances. So they soon become tired and 
ache. In reading while lying down, the eyes must look toward the 
feet. The constant strain of turning the eyes down tires the muscles, 
so that the vision becomes blurred. 

622. Diseases of the eye. — An ulcer or scar upon the cornea, 
closure of the pupil, cataract, and wasting of the optic nerve are com- 
mon causes of blindness. The conjunctiva of the lids may become 
inflamed and run matter, or may become raw as in graimlated lids. 
All matter should be kept from the eye by washing it off" with borax 
water. 

A particle of sand or other substance between the eyeball and the 
lids causes great pain. Rubbing the eyelid forces the particle into the 
delicate flesh and increases the pain. If the lid is gently held away 
from the eyeball for a moment, the tears may wash out the particle. 

Blows upon the eye are seldom dangerous, for the sclerotic coat is 
the strongest tissue in the body. 



342 APPLIED PHYSIOLOGY 

623. Illusions of sight. — Irritating the optic nerve 
excites the sensation of light. A blow upon the head 
causes a sensation of seeing bright stars. Pressure upon 
the eyeball causes a sensation of a ring of light. 

In dreams, sight memories return to consciousness with 
all the vividness with which they were first made. A 
crazy man may imagine the face of the clock to be a 
man's face mocking him, and so he may attack and 
destroy it. To insane persons of a religious turn of 
mind, a cloud may seem to be an angel urging them on 
to some inspired mission. 

624. Effects of alcohol and tobacco. — Alcohol weakens 
the optic nerves, and tends to cause dimness of vision 
while the eyes may appear healthy. Tobacco has a still 
greater effect upon the optic nerve. 

625. X rays. — In December, 1895, a kind of light pro- 
duced by electricity was discovered which can penetrate 
wood, flesh, and other substances. By means of it photo- 
graphs can be taken. Although it makes no impression 
upon the retina, yet by passing it through certain sub- 
stances the rays become visible to the eye. Bone is pene- 
trated by the rays with greater difficulty than flesh, and 
so they can be photographed and seen within the body. 
These rays cannot be bent from their course, and so can- 
not be brought to a focus to produce a real image ; but 
images of objects are formed in shadows, due to the vary- 
ing degrees of light which passes through different objects. 
The rays are sometimes called Rontgen rays from their 
discoverer, and sometimes simply X rays because of their 
unknown nature. Practical use of the rays is made in 
looking within the body so as to determine by sight the 
condition of the bones and the location of substances 
imbedded in the flesh. 




A foot in a shoe. 
(From an X ray photograph.) 




344 APPLIED PHYSIOLOGY 

626. The eye in lower animals. — In all fourfooted animals, 

and in birds, reptiles, and fishes, tlie eyes are essentially the same as in 
man. 

Most insects possess large immovable eyes shaped like a dome. Each 
eye is made up of many smaller eyes like a honeycomb. Each little 
eye contains a lens which forms an image 
upon the nerve at the bottom of the cavity. 
In some lower forms of animals, like the 
leech, there is a spot of dark coloring matter 
under the skin in which the nerves of sight 
end. Such eyes cannot form an image, on 
account of the absence of the lens, but a 
bright light or a shadow of a large object 
can affect the nerve and give the leech 
The eye of a house fly. ^^^^ -^^^^ ^f its surroundings. Some still 
a eye, made of many small i^^^^^ ^^^^^^ of animals seem to be able to 
recognize light, for they fold themselves up 
when darkness comes, and yet they have nothing which at all re- 
sembles an eye. 

Some plants, like the morning glory, are affected by light, for their 
flowers fold themselves at night and open again when the sun 
rises. 



SUMMARY 

1. Light is the name given to the vibrations of a very 

rare gas which fills all space. 

2. The eye is Uke a photographer's camera. 

3. The eye is set deep in a bony socket, called the orbit, 

and is protected in front by the lids, and moistened 
by tears. 

4. The eye can see distinctly only a small space directly 

in front, but can distinguish the presence of objects 
in a full half circle. 

5. A sensation of sight is produced instantly, but persists 

for one tenth of a second after the light disappears. 

6. Some eyes cannot see some colors, especially red. 



THE EYE 345 

7. If the lens cannot bring the rays of light together, a 

person is far-sigJited, but if it brings the rays to- 
gether too soon, he is ncar-sigJited. If it brings 
some of the rays together sooner than others, the 
condition is called astigmatism. 

8. If the lens does not permit light to pass through, the 

condition is called a cataract. 

9. By means of the two eyes viewing an object from 

slightly different positions, we form an idea of 
position and solidity. 

10. If one of the muscles of the eye pulls the eyeball 
to one side, the person is cross-eyed and sees two 
objects instead of one. 

12. Irritation of the optic nerve causes a sensation of sight 
as though light had caused the impression. Mem- 
ories of sight may be recalled so vividly as to seem 
real, as in a dream. 

DEMONSTRATIONS 

135. Examine the eyeball of a calf in its socket. Carefully sepa- 
rate the eyeball and its muscles and nerves from the fat. Notice the 
cushion of fat surrounding the whole eyeball. Notice the slender mus- 
cles which arise from the back part of the orbit and are attached to the 
outer edge of the eyeball. Notice the optic nerve entering the middle of 
the back side of the eye. Notice other nerves and the numerous blood 
tubes which cross the space. Preserve the specimen in Muller's fluid. 

136. Procure several eyes removed from their sockets, and place 
some in Miiller's fluid for a week or two, and examine others fresh. 

Notice the bulging and clear cornea, and the tough white sclerotic 
coat. Holding the eye with its cornea toward you, cut it completely 
into halves. Notice the aqueous and the jellylike vitreous humors. 
Notice the curtain of the iris and its pupil. Behind the iris notice the 
lens. Remove the lens and note its shape and its firm consistency. 
Notice the black choroid coat lining the eyeball next to the sclerotic. 
Notice the thin retina, which readily separates from the choroid. 



346 APPLIED PHYSIOLOGY 

137. With a common magnifying glass show how a convex lens 
brings rays of sunlight to a focus. Show also a photographer's camera. 
Show the image which appears upon the ground glass. Then compare 
the camera with the eye specimen, pointing out the resemblances. 

138. Have the students look steadily at a line of print and tell how 
much they can read without moving their eyes. An inch and a half 
will be all they can see at once. 

Next have them look steadily at an object, and notice how they can 
see dimly all objects in a semicircle about them. 

139. Illustrate the duration of impressions by spinning a square top. 
It will appear circular. 

140. Illustrate the exhaustion of the retina by having the students 
gaze at a square of black cloth upon a white paper. After a moment 
let the students look steadily at the wall, when a square spot of light 
will appear, for the part of the retina upon which the image of the 
cloth fell is less exhausted than the rest, and so it sees the light from 
the wall more clearly. 

141. Illustrate color bHndness by taking a sheet of light pink paper. 
Have the students first look steadily at a bright red object in a strong 
light. Then gaze at the pink paper ; a green image of the first object 
will appear, showing that a part of the retina has become exhausted for 
the red rays, but can still see other colors. 

142. Notice the pupil of the eye and its varying size in different 
lights. Shade another person's eyes with the hands, and, quickly 
removing them, notice that the pupils grow smaller. Have a person 
look steadily at your finger held a few feet in front of the eyes, and 
then quickly bring the finger near the eye and notice that the pupil 
contracts while looking at it near by. 

143. Illustrate a near-sighted eye by holding a magnifying glass in 
front of the eye, which is the same as increasing the power of the lens. 
Notice that the object must be brought nearer the eye. 

^ Show a double concave lens and explain that it scatters rays and so 
is used in glasses for near sight. 

144. Illustrate far vision by looking through two magnifying glasses 
of different strengths. Notice that the weaker glass must be held 
farther away from the object. 

145. Place a book edgewise before the eyes and notice that one eye 
sees one side and the other eye the other side. 

Now examine a stereopticon photograph of a statue, and notice that 



THE EYE 347 

the two pictures are not exactly alike. When the views are blended 
into one by the stereopticon, the image seems to stand out like a real 
statue. Explain that in this way the two eyes gain a knowledge of 
position and solidity. 

146. Illustrate double vision by pressing one eyeball aside while 
looking at an object. 

147. Have a person gaze at your finger held at a distance from his 
eye. Now bring the finger near the eye, and notice that the eyes each 
turn towards the nose so as to keep directed toward the object. This is 
the only manner in which we can move the eyes in opposite directions. 

148. Press hard upon the closed eyelids. Notice the ring of light 
which appears. Explain that this is due to the irritation of the optic 
nerve. 

149. Test the individual members of the class for color blindness 
by showing them shades of red, green, and yellow, telling them to 
match the shades and arrange them in order. Also test the power of 
vision of the individual members of the class by placing before them 
printing with letters of \'arious sizes. Have each pupil read as far as 
he can, all standing at the same distance. 



REVIEW TOPICS 

1. Describe light; color; focus; and the effects of light 

in a photographer's camera. 

2. Show that the eyeball is like a photographer's camera, 

describing its outer coverings ; its retina ; nerve ; 
cornea ; iris, pupil, and lens. 

3. Describe the orbit ; eyelids ; the lachrymal gland ; 

tears, and the tear ducts. 

4. Show that a person can see more clearly directly in 

front of his eyes than upon either side. 

5. Show that the duration of a sight sensation changes 

the appearance of moving objects. 

6. Describe color blindness. 

7. Show that the retina may become unable to act from 

overwork, as by gazing at bright objects ; at colored 



348 APPLIED PHYSIOLOGY 

objects; and by a light in front of the unshaded 
eyes. 

8. Show that the iris protects the retina against too 

strong light. 

9. Show that the lens must change its shape to accom- 

modate itself to near vision and to far vision. 

10. Tell the condition of the lens and the remedy mfar 

sight ; in near sight ; and in astigmatism. 

11. Describe a cataract and its remedy. 

12. Show how two eyes aid in the judgment of form and 

position. 

13. Describe the condition of the eye muscles in a cross- 

eyed person, and tell how vision is affected. 

14. Show how reading upon a moving railway train and 

reading while lying down overwork the eye mus- 
cles. 

15. Tell how to care for an eye which runs matter, and 

how to remove a speck of dirt from under the lid. 

16. Show that rubbing a sore eye is always liable to do 

harm. 

17. Show that irritation of the eye may produce false 

sensations of sight ; and that sight memories may 
seem to be real again. 

18. Describe the X rays, 

19. Describe the effects of alcohol and tobacco on the 

eye. 

20. Describe the eye in lower animals ; in insects ; and in 

a leech. 



CHAPTER XXXVI 



THE VOICE 




627. The larynx. — The basis of the voice is a sound 
made in the larynx during expiration. The larynx is a 
triangular box about three quarters 
of an inch across, made of cartilages. 
It connects the trachea and pharynx. 
Its two sides are formed of a flat 
cartilage, bent sharply backward, 
and called the tliyroid cartilage. 
The upper end of the fold projects 
slightly from under the chin and is 
called the Adams apple. Under- 
neath the thyroid cartilage is a cir- 
cular cartilage whose back part pro- 
jects upward so as partly to fill in 
space between the back edges of 
the thyroid cartilage. In form and 
size it resembles a larg^e fins:er ring:, ^ c^\^o^d cartilage. 

^ ^ ^^ e epiglottis, 

and is called the cricoid cartilage. 

On top of the back "part of the cricoid cartilage are two 
small cartilages, shaped like triangular pyramids, and so 
arrano;ed that thev can turn sidewise. One lower corner 
of each projects forward. From it a flat band extends 
across the larynx, and, with its fellow from the opposite 
side, attaches itself to the lower part of the thyroid carti- 
lage. Muscles can tighten them and bring them close 

349 



Back view of the larynx. 

a thyroid cartilage. 

b vocal cords. 

c movable cartilage for the 

attachment of the vocal 

cords. 



350 



APPLIED PHYSIOLOGY 



together. Expiring air between these bands, while they 
are tight and close together, causes them to vibrate and 
produce a sound which is called the voice. Hence the 





Top view of the larynx, with the 
vocal cords closed, as in speaking. 

a epiglottis. b vocal cords. 



Top view of the larynx, with the 
vocal cords open, as in breathing. 

a epiglottis. b vocal cords. 



bands are called the vocal cords. The whole larynx, ex- 
cept the edges of the vocal cords, is covered with loose 
mucous membrane. 

628. Pitch of the voice. — All sound has the four char- 
acteristics of pitchy intensity, quality, and din^ation. The 
same characteristics apply to the voice. 

Pitch depends upon the number of vibrations which 
occur each second. In order that the vibrations of the 
air shall blend into a musical note they must occur at the 
rate of sixteen times a second, but until they reach a rate 
of fifty the sound is more like a buzz than music. Upper 
C of the bass voice which corresponds to lower C of a 
soprano, is produced by 256 vibrations per second. The 
shorter or tighter the vocal cords are, the higher will be 
the pitch. In men the cords are longer than in women, 
making a man's voice an octave lower in pitch. The 
larynx and voice of a boy resemble those of a girl. At 
about the age of fifteen the voice of a boy becomes like 
a man's, while in a girl it remains unchanged, 

629. The intensity of the voice depends upon the force 
with which air is expelled through the larynx. In making 



THE VOICE 351 

a very loud sound, the great force of the air current causes 
the vibrations of the vocal cords to be painful. 

630. The muscles of the larynx will grow strong by judicious prac- 
tice, so that a person can be heard across a hall in which he formerly 
could not be heard a few feet away. If the voice becomes husky, or 
causes a cough, or if the throat begins to feel painful, the vocal cords 
are being overworked and should be rested. 

631. Quality of the voice. — A string stretched between 
the hands produces a faint unpleasant sound ; but if it is 
stretched over a hollow box, like the body of a violin, the 
whole box will vibrate and greatly magnify the sound and 
also will make it full and pleasant. 

The vibrations of the vocal cords alone produce a faint 
and almost squeaking sound very unlike that of the voice ; 
but below the larynx are the hollow trachea and lungs. 
Above it are the hollow mouth, nose, and frontal sinuses. 
All these vibrate with the vocal cords, and so the quality 
of the voice is modified. Each person's voice has a peculiar 
quality of its own which is at once recognized. 

When a person sings with the nose stopped, we say 
that he sings through the nose. In reality, a nasal voice 
is due to the absence of vibrations in the nose. 

632. Ventriloquism. — The quality of sound is modified by 
distance, so that one can judge accurately whence it comes. It is 
possible to imitate the quality of distant sounds, so that there seems to 
be another person talking in a remote part of the room or inside of the 
real talker. This is called ventriloquism. 

633. Speech. — Speaking consists mainly in rapid changes 
in the quality and duration of vocal sounds. In singing or 
crying out, single sounds are more or less prolonged, but 
in forming spoken words, the sounds are cut off by the 
tongue and lips several times a second. It is not even 
necessary to form a sound with the larynx. In whispering, 



352 APPLIED PHYSIOLOGY 

air is simply breathed through the mouth, while the tongue 
and lips cut it off at intervals as though a sound were 
being made. 

634. A simple sound continuously uttered is a vozvel 
sound. If the mouth is simply opened without effort, the 
sound formed will be that of a as in father. When the 
mouth is closed the most, it forms the sound oo as in room. 
A consonant sound is a vowel sound suddenly modified in 
either its beginning or ending. For instance, when the 
tip of the tongue is held against the palate just back of the 
teeth, and a vowel sound is begun by forcibly blowing it 
away, the sound will be either t, d, or th. 

635. Rate of talking. — A public speaker will ordinarily utter 
125 words a minute. On an average each word will be composed of, 
at least, four different sounds. Thus the vocal organs must make 600 
separate adjustments each minute, or 10 each second. 

636. Relation of sound and speech. — Words spoken must 

first be heard. So no matter what the race of a child, it will speak 
exactly the speech which it hears. If a child is brought up in com- 
pany with an ignorant nurse girl, its speech will be her brogue. On 
the other hand, if the child is brought up among educated and refined 
persons, it will speak an elegant tongue. 

A deaf person has great difficulty in learning to speak at all, for he 
can have no idea of the sound which he should make. Without special 
instruction deaf persons would never learn to speak at all, but by letting 
them see or feel the position of the lips and tongue in forming words, 
they learn to place their own parts in the same position and so finally 
learn to talk. 

637. Necessity of the tongue in speech. — The tongue is 

usually considered to be so necessary in speech that the language itself 
is called a tongue. As man's mouth is constructed the tongue does do 
the most important part of forming words, but if the organ is removed 
as far back as possible, the stump can still form intelligible words. 
Sometimes the front part of the tongue is bound down or '' tied " so 
that it cannot move so freely as it should. This is supposed to hinder 
a child in talking, but in reality it does not. 



T^HE VOICE 353 

638. Benefits of vocal exercise. — In singing and lec- 
turing, the breathing must be regular and deep. The 
abdominal muscles must act, and often a sound must be 
prolonged until the air in the lungs is exhausted. The 
respiratory muscles must act continuously and strongly 
and for long periods of time. Thus an increased amount 
of oxygen will be taken into the body. Voice training is 
one of the best modes of exercise, especially for a weak 
person who cannot endure long walks or gymnastic exer- 
cises. It is all the more valuable because a person does 
not think of the exercise, but directs the mind to an inter- 
esting and useful occupation. 

639. Diseases of the larynx. — In a cold in the throat 
the mucous membrane becomes tender and swollen. Then 
the movements of the vocal cords are impeded and painful, 
so that only a hoarse sound, or no sound at all, can be 
produced. By repeatedly overworking the vocal cords, 
they and the muscles of the larynx become flabby and 
tender so that their vibrations are painful or impossible. 
Then the voice is reduced to a whisper. Sometimes the 
nerves of the larynx are paralyzed so that no motor orders 
can reach the muscles. Then no sound can be formed. 

640. In mouth breathing, the air is drawn directly into the lar3'nx 
without being purified, warmed, and moistened in the nose. This irri- 
tates the larynx and vocal cords so that the voice is made weaker and 
harsher. A mouth breather can seldom become a good singer or 
speaker. 

641. Tobacco. — Tobacco smoke may produce such an 
irritation that there is a constant hacking cough. Cigar- 
ettes are especially bad for the voice, for the smoke is 
deeply inhaled. Alcohol interferes with the voice by 
inducing indigestion and weakness of the muscles. 

OV. PHYSIOL. — 23 



354 APPLIED PHYSIOLOGY 



SUMMARY 

1. The larynx is a box of cartilage across which two 

strong bands called vocal cords are stretched. 

2. When the vocal cords are tightened and air is expelled 

between them, a sound called the voice is made. 

3. The pitch of the voice will depend upon the tightness 

and length of the cords. 

4. The intensity of the voice depends upon the force 

with which the air is expired. 

5. The quality of the voice is imparted to it by vibrations 

of the air in the lungs, mouth, and nose. 

6. In speech sounds are modified mainly by the lips and 

tongue. 

7. A man must first hear the sound of speech, and then 

learn to imitate it. Special means must be employed 
to teach a deaf person to talk. 

8. If the vocal apparatus is overworked or becomes 

inflamed, the voice is injured. 

DEMONSTRATIONS 

150. Procure a larynx from a butcher's shop. Notice the large flat 
thyroid cartilage, and under it the ring-shaped cricoid cartilage. Notice 
the white vocal cords passing forward to the lower part of the thyroid. 
Notice the loose mucous membrane above the vocal cords. Grasp the 
thyroid cartilage so as to move the cricoid forward and backward, and 
note how the movements tighten and relax the vocal cords. Notice 
the muscles which move the larynx. Test the pyramidal cartilages to 
which the vocal cords are attached. 

151. If possible, get a. physician to show the vocal cords in action 
upon a living person. He will do it by means of a small mirror held 
in the back part of the mouth. 

152. Have the pupils feel each other''s chests while counting one, 
two, three, and note the marked vibrations. In the same way feel of 



THE VOICE 355 

the larynx and of the nose and teeth. Explain that these vibrations 
also produce sound and give qualit}' to the sound in the lar3nx. Then 
compress the nose and note the nasal quality of the voice. 

153. Show how the different vowel sounds are formed. Make a con- 
tinuous sound as of e in need. Without changing the pitch or intensity 
change the mouth to a position to utter in succession the sounds a as 
in 7nade, a as in ;nat, ah as in father, o as in note^ and 00 as in ?-oom. 
Note how the sounds glide into each other. 

154. Note the positions of the tongue and lips in uttering the 
different consonant sounds. Note that p, b, and f are formed much 
alike ; and also k, ch, and^'; and t, d, and th. 

155. Show how some lower animals and insects produce sounds. 
Have the pupils notice how a canary bird swells his throat in singing, 
and explain that this is because it has two or three pairs of vocal cords. 

Upon the backs of a katydid's wings show the drumheads, which, 
when rubbed together, produce its sound. Show that a fly's buzz is 
due to the exceedingly rapid motion of its wings. 



REVIEW TOPICS 

Describe the larynx. 

Show how the vocal cords produce sound. 

Show how the pitch of the voice can be changed. 

Show how the intensity of the vocal sounds can be 

changed. 
Show how the qnality of the voice is modified. 
Describe ventriloquism. 
Show that speech depends upon modifications in the 

duration and mode of production of vocal sounds. 
Show the relation between speech and hearing. 
Show that the tongue is not absolutely necessary in 

speech. 
Show how vocal exercise benefits the whole body. 
Show how inflammation of the larynx and taking 

certain things into the mouth injure the voice. 



Bones of the 



Clavicle, or Collar Bone. 



Sternum, or Breastbone. 



Ribs. 



Pelvis, including (5.) Sacrum and 
(Cx.) Coccyx, 




Head and Face. 



Bones of Vertebral Column. 



Scapula, or Shoulder Bone. 



Humerus. 



Ulna. 



Radius. 

Carpus, or Wrist. — Eight 

small bones. 
Hand. — Nineteen bones. 



Femur. 



Patella 



Tibia, or Large Bone of Fore Leg, 



Tarsus, or Ankle and Heel Bones (7). 
Bones of foot. — Nineteen bones. 




Fibula, or small Splint Bone of Leg. 



The human skeleton, showing position of bones. 

356 



CHAPTER XXXVII 

BONES. 

642. Use of bone. — Bones give shape and support to 
the body and impart to it strength and stiffness. Like 
beams of the strongest oak, they extend the length of 
every Umb, and form arches for the protection of the 
organs in the head, chest, and abdomen. They are of va- 
rious sizes and shapes, as are suited to the different parts. 
In the whole body, about two hundred are jointed together 
to form its framework, called the skelet07i. 

643. The skeleton. — Eight rounded plates of bone form 
the top of the head, and fourteen of irregular shape form 
the face. Together, they form the skull. 

Twenty-six irregular rings of bone piled one upon the 
other form a support for the trunk of the body. It is 
called the backbone or spinal column, or simply the spine. 
The lowest bone is called the coccyx, and the one next 
above it, the sacrum. Each ring of bone is called a verte- 
bra. The spine is made of a series of small bones so that 
it can bend without breaking. It is gently curved so as to 
lessen the jarring in running and other violent movements 
of the body. 

From the vertebrae, beginning at the eighth, twelve pairs 
of bones called ribs curve around the body. In front they 
join a fiat bone called the stermim or breastbone. They 
inclose and protect the heart and lungs. 

Each shoulder is formed in front by a slender bone 

357 



358 



APPLIED PHYSIOLOGY 



called the collar bone or clavicle, and behind by a flat bone 
called the shoulder blade or scapula. Their outer ends 
meet and form a support for the arm. 

The upper arm has one long bone 
called the humertts. The forearm has a 
long bone on its thumb side called the 
radius, and another on its little finger side 
called the ttlna. The wrist has eight 
rounded bones called carpal bones. The 
palm of the hand has five long bones 




The pelvis. 



called metacarpal bones. The fingers have 
fourteen slender bones called phalanges. 

Two irregular and massive rings of 
bone form the hip bones. With the sa- 
crum they form a ring called the pelvis. 
The body sits upon the lower part of 
each hip bone. The pelvis forms the 
bottom of the abdomen. 
The bones of the leg have nearly the same plan and 
arrangement as those of the arm. The thigh has one long 
bone called the femur. In front of the knee is a flat bone 



The spinal 
column. 



BONES 359 

called the patella. The shin is formed by one long bone 
called the tibia, upon the outside of which is a very slender 
bone called the fibula. The lower end of the fibula forms 
the outer ankle bone, while a projection from the tibia 
forriis the inner ankle bone. 

Seven rounded bones, called tarsal bones, form the instep 
of the foot. Five slender bones beyond them, called nicta- 
tarsal bones, form the ball of the foot. The tarsal and meta- 
tarsal bones are bound together so as to form an arch 
which bears upon the ground only at the heel and ball of 
the foot. The arch is somewhat elastic and prevents jar- 
ring of the body in walking. It sometimes becomes flat- 
tened, producing the painful deformity called Jlat foot. 
Fourteen slender bones, called phalanges, form the 
toes. 

644. Structure of bones. — Bones are dense and brittle 
upon the outside. All are covered with a very tough mem- 
brane, called \^\^ periosteum. In flat or rounded bones the 
hard outside surfaces are scarcely thicker than paper, and 
the two surfaces are connected together by a network of 
bone which looks like a honeycomb, and is called cancel- 
lous bone. 

In long bones, the central shaft is composed of a thick 
shell of hard bone surrounding a cavity filled with fat; 
their ends consist of a thick shell of hard bone covering a 
large mass of cancellous bone. 

A bone is about twice as strong as a piece of oak of the same size. 
It is elastic and can bend considerably without breaking. Any given 
weight of a substance is stronger when made into a hollow shaft, like 
a bicycle frame, than when formed into a solid rod of the same length. 
So the strength of a bone is still further increased by its being either 
hollow, as in the shaft of a long bone, or else braced with cancellous 
bone, as in a flat bone and the ends of a long bone. 



36o 



APPLIED PHYSIOLOGY 



645. Microscopic appearance. — Bone is composed of\ 
branching connective tissue cells and iibers, which are 
arranged in circles around minute tunnels called Haversian 
canals. Each Haversian canal contains arteries, veins, 
and nerves. Lime is mixed with the cells and canals like 
starch among the fibers of linen, and imparts to them their 




a bone cells. 



Thin slice of bone (x 200). 

b Haversian canal, containing blood tubes and nerves. 



hardness and rigidity. Lime forms about two thirds of 
the bone by weight. 

646. The periosteum carries arteries and nerves which 
enter minute openings in the bone. During childhood, or 
when a bone is diseased, the cells of its inner layer are 
very active in reproducing themselves and in forming new 
bone. Bone stripped of its periosteum is apt to die, 
but when the bone dies the periosteum usually remains 
alive and soon reproduces new bone. The periosteum 
also affords an attachment for muscles. 

647. Cartilage. — The bones of very young animals 
contain little or no lime, but are soft and pliable. In this 



BONES • 361 

condition they are called cartilage. As age advances, 
lime is deposited among the cells, and they become hard 
and brittle, forming true bone. A layer of cartilage re- 
mains to cover the ends of most bones. Late in life it 
may take up lime and so become like bone. 

648. Rickets. — Sometimes a child's bones contain too little lime ; 
then under the influence of continual pressure of standing, the bones of 
the leg may gradually grow into a bowed shape. This disease is called 
rickets^ and is due to too little nourishment. When fed on a sufficient 
amount of proper food, the bones soon grow rigid again, and as the 
child's legs grow longer, their curves become less noticeable. 

649. Broken bones. — Bones are often broken. Then 
the cells are injured, and blood tubes and nerves are torn 
across. So there will be great pain and tenderness. When 
a bone is broken, its cells reproduce themselves and fill in 
the space with new connective tissue. In course of a 
few weeks, lime is deposited in the new tissue, and the 
union is complete. When a bone is broken, the surgeon 
pulls its ends in place and binds them to stiff splints until 
healing is complete. 

If a bone is broken, the limb should be at once bound to a board or 
stick with handkerchiefs or strips of cloth. Take care not to tie the 
bands tightly enough to stop the flow of blood. 

As a person grows older, more lime is deposited in his bones, and 
they become harder and more brittle. Then they are more likely to be 
broken and are less aHle to grow together again. Often a child's bone 
will bend until it breaks, but its ends still hold together like a broken 
green stick. In older people it snaps like a dry twig. 

650. Diseases of bones. — Bruises or consumption or other 
causes of disease may produce inflammation and abscesses of the bone 
as in any other part of the body. Then the bone is very painful and 
tender and may cHe. Then the periosteum will form a new bone. If 
a large piece of bone dies, it wastes away more slowly than new bone 
is formed. All fourfooted animals have nearly the same bones arranged 



362 APPLIED PHYSIOLOGY 

in the same way as man. A bird's wing is bone for bone almost like a 
man's arm and hand. A turtle's shell is its ribs, while the bones of its 
limbs are like those of man. 

SUMMARY 

1. About 200 bones give the body form and strength. 

2. The outside of all bone is a hard plate, while the inside 

is either a fine network of bone or else is hollow. 

3. The hollow form of bone combines strength with light- 

ness. 

4. Bone is composed of living cells and fibers nourished 

by arteries and endowed with sensibility by nerves. 
Lime is mixed with the cells like starch with linen. 

5. Bone is covered with a tough membrane called the/^n- 

ostenni, which carries the blood tubes and nerves to 
the bone, and forms new bone during the period of 
growth or when the bone is diseased. 

6. Cells and fibers resembling those in bone, but contain- 

ing no lime, form cartilage. 

DEMONSTRATIONS 

156. Show a complete skeleton of at least a small animal. Point 
out the different shapes of the bones and how they are adapted to their 
positions and work. Point out in the living body where the different 
bones can be felt. 

157. Procure a fresh beef bone, and another similar one dried. Note 
the bright pink color of the fresh bone, and the white or brown color 
of the dried specimen. Notice that the periosteum can be stripped 
from the bone. Notice the soft cartilage which covers the ends of the 
bone. 

158. Saw a long bone in two crosswise and then saw one half in two 
lengthwise. Notice the hollow cavity in the shaft of the bone and the 
fat or marrow which fills it. Notice the honeycombed appearance of 
the inside of the ends of the bone. 

159. Procure a specimen of bone mounted for the microscope. 
Using a power of at least fifty diameters, notice the circles of bone cells 



BONES 363 

and the numerous fine branches of the cells. Notice the Haversian 
canal in the center of each circle. Examine also a specimen of 
cartilage. 

160. Procure two slender bones which are exactly alike. Place one 
in a hot fire for a few hours. This will burn out the cells and fibers 
and leave only the lime. The bone is now very brittle and easily crum- 
bles to pieces. Place the other in a bottle containing one part of 
muriatic acid and ten of water. After a week this acid will have 
removed the lime, leaving only the cells and fibers. The bone can now 
be twisted and bent like a piece of flesh. 

161. Boil a leg bone of a half-grow^n animal until the flesh is re- 
moved. Notice that a disk of cartilage extends nearly through the 
shaft very near the ends. Possibly the end beyond it will come off. 
Explain that the cartilage forms new bone which increases the length 
of the shaft as long as the bone continues to grow. 



REVIEW TOPICS 

1. Show why bones are needed in the body. 

2. Describe the bones of the skull; of the spine; of the 

ribs ; of the arms ; of the pelvis ; and of the legs. 

3. Describe the appearance of a bone when sawed in two 

both lengthwise and crosswise. 

4. Show the advantage of having some of the bones 

hollow. 

5. Describe the microscopic appearance of bone. 

6. Give the uses of periosteum. 

7. Describe cartilage. 

8. Describe the changes which occur in bones with ad- 

vancing age. 

9. Describe rickets. 

10. Describe the condition of a bone when broken, and 

tell how it is repaired, and how to care for a broken 
limb. 

1 1. Show how a bone can become inflamed ; and how dead 

bone is replaced. 



CHAPTER XXXVIII 



JOINTS 



651. Kinds of joints. — The union of two bones is called 
a joint. Some bones grow together and form a single 
rigid bone, while others are joined together only by loose 
fibrous tissue which permits the joints to bend freely. 
Between these two* extremes, joints possess all gradations 
of movement. 

652. Inflexible joints. — Some bones of the skull are 
joined together by cartilage during childhood. Later in 

life, when growth ceases, the cartilage 
becomes bone and unites the two bones 
into a single one. 

Other bones of the skull are dove- 
tailed with each other, so that while 
they can move slightly, they cannot be 
separated. The thick bones of the top 
of the skull are united in this way. 

Between the separate bones of the 
pelvis and between the vertebrae there 
are large pads of fibrous tissue, almost 
like cartilage. These pads permit slight 
movements between the bones and so 
prevent jarring during violent move- 
ments of the body. They are usually stronger than bone 
itself, so that, by pulling or bending, the bones will be 
torn apart rather than the pads. 

364 




Hinge joint of the elbow 

I humerus. 2 ulna. 



JOINTS 365 

Between the ends of the ribs and the sternum there are 
cartilages of the shape of the ribs. In old age they often 
take up lime and become real bone. 

653. Flexible joints. — The joints of the head and trunk 
of the body are mostly inflexible, while those in the limbs 
permit very free movements of the bones. In flexible 
joints the bones are held together by a strong fibrous 
membrane called a ligament. The ends of the bone are 
smooth and rounded so as to move freely upon each other. 

In some joints the movements are simply forward and 
backward like a hinge. The fingers, toes, elbows, knees, 
and ankles are hinge joints. 

In some joints the movements can be made forward and 
backward and sideways like a ball in a socket. The 
thumbs, great toes, shoulders, and hips have this kind of 
a joint. In each the end of one bone is spherical and fits 
into a hollow socket in the other. 

In other joints one bone can only rotate about another 
as a pivot. In its union with the spine, the skull turns 
about a fingerlike projection upon the top of the second 
vertebra. At the elbow, the upper end of the radius 
turns m a socket upon the side of the ulna through half 
a circle of revolution. 

654. Structure of joints. — In all flexible joints the liga- 
ments pass from bone to bone, like a collar upon the out- 
side of the bone, enveloping a cavity which is lined with 
a thin and smooth membrane, called synovial membrane. 
The synovial membrane secretes a fluid like the white of 
an ^gg, called the synovial fluid. The fluid moistens and 
lubricates the joint so that it turns smoothly and easily. 
If it is absent the joint creaks when moved. 

655. Loose joints. — The two bone surfaces of each joint fit 
together accurately. There is a considerable difference in the depths 



366 APPLIED PHYSIOLOGY 

of the joint sockets and in the lengths of the Hgaments in different per- 
sons. In some persons the sockets are shallow and the ligaments long, 
so that the joints can be bent to a far greater degree than usual. These 
persons are able to twist and contort themselves into strange posi- 
tions and shapes, and thus they make good circus actors. 

656. Action of muscles as ligaments. — Nearly every 
joint is crossed by muscles. By their pressure the mus- 
cles aid in keeping the bones in place. In addition, when 
one muscle acts, those upon the opposite side of the joint 
also contract enough to prevent the head of the bone from 
being drawn out of its socket. 

If all the muscles and cords about a joint are cut, the 
ligaments stretch and the joint becomes loose and flabby. 
If the ligaments are cut while the muscles and cords are 
left, the joint remains snug and firm. 

657. Effects of pressure. — After being kept in an un- 
natural position for some time, joints tend to retain the 
deformity. In wearing tight shoes, the great toes are 
bent outward, while the little toes are bent inward. If 
the joints are kept in this position day after day for years, 
they remain permanently fixed in the deformed position. 
The great toe joint may be tender, forming a bimion. 

658. Curvature of the spine. — The spine is naturally straight 
from side to side. Strong muscles aid in keeping the head erect and 
the shoulders thrown well back. By weakness of the muscles or by 
carelessness the shoulders fall forward, increasing the natural curve of 
the spine so that a person becomes round shouldered. 

If a child habitually sits sidewise at the desk, leaning continually 
upon one arm, the growing bones and the ligaments of the spine will 
gradually become fixed in the deformed position, which persists all 
through life. Any person who, in his occupation, always assumes the 
same attitude, may finally be unable to remove the curvature from his 
spine. On the other hand, if one acquires a habit of sitting and walk- 
ing and working in an erect position, the spine will grow in a natural 
curve. 



JOINTS 367 

659. Sprains. — When a joint is bent to a greater ex- 
tent than is natural, the Hgaments and muscles are 
stretched and often torn. Then there will be great 
swelling and pain. When this accident happens, the 
joint should at once be put in water as hot as can be 
borne, while more hot water is added from time to time to 
keep up the temperature of the water. The joint should 
have rest for some time after the injury. Recovery is 
apt to be slow. 

660. Dislocations. — When the bones of a joint are 
forced apart, the joint is dislocated, or out of joint. 

In a dislocation, the ligaments are always torn. Then 
bleeding will take place, and there will be great pain and 
swelling, while only slight movements of the limb will be 
possible. 

In a dislocation, the muscles around the joint are irri- 
tated, and so contract and hold the bone away from its 
socket. Often it is necessary to make a person insensible 
with ether before the muscles will relax enough to get the 
joint in place. 

When a joint is dislocated, the limb should be kept as 
quiet as possible by binding a splint above and below the 
joint, as in a broken bone. 

661. Inflammation of joints. — Sometimes the synovial mem- 
brane becomes inflamed and pours out a quantity of thin fluid which 
distends the joint and produces great pain. In rheumatism this often 
occurs. Sometimes a blow or a wrench may cause it. 

Sometimes waste matter of the body is deposited in the synovial 
membrane and cartilage. This produces great pain and tenderness 
and constitutes an attack of gout. The great toe joint is especially 
liable to this disease. 

Sometimes the cartilage and ends of the bone become distorted and 
rough, or form hard swelhngs. Then the limbs cannot be bent without 
producing pain and a creaking sensation. This change naturally occurs 



368 APPLIED PHYSIOLOGY 

in old persons, and is due partly to deposits of lime in the cartilage and 
partly to a dry state of the synovial membrane. 

Sometimes a joint slowly swells and discharges yellow matter for a 
long time, while the sufferer gradually loses flesh and strength. The 
disease is commonly known as a white swelling, but is really tuber- 
culosis, or cousumption of the joint. When it affects the hip joint, it 
is called hip joint disease. A form of the disease without the discharge 
of matter may affect the spine and produce the deformity called a 
hunchback. 

SUMMARY 

1. The union of two bones is called 2^ joint. 

2. In joints in which the bones do not move, the bones 

are united either by bone or strong pads of fibrous 
tissue, or by cartilage, or by being dovetailed into 
each other. 

3. In flexible joints, bones are joined together by a collar 

of fibrous tissue and by the action of muscles. 

4. Flexible joints are lined with synovial membrane, which 

secretes a fluid like the white of an ^^^ to lubricate 
the joint. 

5. By assuming one position day after day the joints 

become fixed in that position. 

6. In sprains and dislocations the ligaments are stretched 

or torn, and require long rest in recovery. 

7. The synovial membrane may become inflamed and 

swollen. 

8. A joint may become affected with tuberculosis, forming 

a white sivelliitg or hip joint disease. In it the joint 
forms an abscess and often discharges matter. 

DEMONSTRATIONS 

162. A fowl dressed for the table will illustrate the different kinds of 
joints. Notice that in some places the muscles unite with the ligament 
and in others simply cross it, usually as a white cord or tendon. Cut 



JOINTS 369 

the ligaments half in two to show the cavity of the joint. Notice the 
smooth and shining appearance of the synovial membrane which lines 
the joint and its slight amount of synovial fluid. Bend the joint back 
and forth to show how the surfaces of the bone fit into each other. 
Sketch a joint. 

163. Notice some of the inflexible joints. In an animal's skull notice 
that the joints are dovetailed together with but little cartilage between. 
Notice the tough pads between the vertebrae, and how they permit the 
spine to bend slightly. Notice that the ribs are united to the sternum 
by flexible cartilage. 

164. To show that muscles and cords act as ligaments, clench the 
flst tightly. Notice that the cords upon the back of the hands tighten, 
as well as those which shut the hand. 



REVIEW TOPICS 

1. Describe and locate the inflexible joints with bony 

union ; with union by cartilage ; with union by pads 
of fibrous tissue ; and with union by being dove- 
tailed together. 

2. Describe and locate hinge joints; the ball and socket 

joints ; and the pivot joints. 

3. Describe the structure of joints, their ligaments, syno- 

vial membrane, and fluid. 

4. Show how muscles aid the action of the ligaments. 

5. Show how long-continued pressure affects the joints, 

as in the great toe. 

6. Show how the position of the body may produce curva- 

ture of the spine. 

7. Describe the nature and treatment of a sprain^ and of 

a dislocation. 

8. Show how joints may become inflamed. 

9. Describe a wJiitc sweili?ig. 
o. Describe a bunion. 

OV. PHYSIOL. — 24 




The muscular system. 
370 



CHAPTER XXXIX 
MUSCLES 

662. Movements within the body. — Every action of the 
body has motion for its basis, and every cell possesses 
motion of some form. But certain cells of the body are 
set apart to produce motion in the various liquids of the 
body and to move different parts of the body itself. Cells 
whose work is to produce motion are called muscle cells. 

663. Involuntary muscles. — Some movements of the 
body go on wholly without our knowledge and are not 
affected by the will. Such are the movements of the 
blood, and of the peristalsis of the intestine. These invol- 
untary movements are produced by muscle cells which are 
governed by the sympathetic nervous system. Each mus- 
cle cell resembles a string with pointed ends. They are 
wrapped around the arteries, intestine, bronchi, 
and other hollow organs. They are inter- 
woven with the other tissues of the organ and 
cannot be recognized without a microscope. 

664. Voluntary muscles. — The muscles which 
enable the body to move are under control of 
the will. They are situated mostly upon the 
outside of the bones, and altogether form over 
one half of the weight of the body. They A muscle ceil 
round out the figure and impart to it strength ^^ ^^^^' 
and beauty. The other organs of the body of man exist in 
order that the brain and muscles may subsist and work 
out the plans of man's higher nature. 

37^ 



372 



APPLIED PHYSIOLOGY 



The lean part of meat is muscle. Each muscle can be 
split lengthwise into bundles again and again until each 
muscle cell is separated from the rest. Connective tissue 
binds the whole together. 

A muscle cell is a cordlike body about -g-J-g- of an 
inch in thickness. Extending 
crosswise upon its surface are 
alternate dark and light bands 
which serve to distinguish a 
muscle cell from all other cells of 
the body. Each cell is surrounded 
but not penetrated by a network 
of capillaries and is held in place 
by delicate fibers of connective 
tissue, which are always small in 
quantity compared with the cells. 
muscles. — One end of a muscular 




Muscle cells cut across 

(X 200). 

muscle cell. 

connective tissue binding the 
cells together. 



665. Attachment of 

bundle is usually attached to the 
periosteum of a bone, while the 
other end is joined to a string of 
connective tissue called a te^tdon. 
A tendon is a white pliable cord 
and «is exceedingly strong. It 
runs in a groove lined with 
synovial membrane, and its end 
is usually attached to a bone. 
A muscle usually forms a 
rounded projection above a 
joint to be moved, while its 
tendons extend across the joint 
and are attached to the perios- 
teum of the next lower bone. This arrangement keeps the 
weight of the limbs near their upper extremities. 




A thin slice of a voluntary mus- 
cle cut lengthwise (x lOo). 



a muscle cell. 

b capillaries surrounding the cells 
c connective tissue binding 
cells together. 



the 



MUSCLES 



373 



666. Contraction of muscles. — When a muscle cell is 
cut or pinched or irritated in any way, it becomes shorter 
and thicker. This is called a contraction, and is the essen- 
tial peculiarity of muscles. An end of a motor nerve 
thread touches every muscle cell and conveys to it orders 
from the cells of the spinal cord and brain. Each order 
causes a contraction. 

A muscle cell requires about -}-^ of a second to contract and another 
2V of a second to become relaxed. So it is impossible to move a limb 
more than ten times a second. The brain sends about ten orders per 
second. Thus before the muscle relaxes it receives another order and 
so remains in a tremulous state of contraction which becomes apparent 
during excitement or when a great effort is being made. Each con- 
traction is a change in the shape and not in the size of the muscle. 






I. II. III. 

The three classes of levers, and also the foot as a lever. 



667. Bones as levers. — A rigid bar turning about a 
fixed point or fulcrum is called a lever. When the weight 
is at one end of the bar and the power at the other end 
while the fulcrum is between the two, the bar is called a 
lever of the first class. 

When the weight is between the power and the fulcrum, 
the bar is called a lever of the jt<:<?;/^ class. 

When the weight is at one end, the fulcrum at the other, 
and the power between, the bar is called a lever of the 
third class. 



374 



APPLIED PHYSIOLOGY 



Muscle. 



Tendon 



If the power is farther away from the fulcrum than the 
weight, it will move a weight greater than itself, but if it 
is a less distance away, it can move only 
a weight less than itself. 

A bone is a rigid bar. The joint is 
the fulcrum upon which it turns. The 
power is the contraction of the muscles 
which are attached to it. The weight 
is the weight of the body or limb to- 
gether with anything which may be 
grasped. 

668. Levers of the first class are not 
numerous in the body. The foot when 
pressing down with the toes, and the 
head when it is raised, are two examples. 

669. Levers of the second class are 
also few. The best example is the foot 
when standing on the toes. The power 
is attached to the heels and is furnished 
by the muscles upon the back side of 
the leg below the knee. They end in a 
very strong tendon called the tendon of 
Achilles, which can be felt under the 
skin above the heel. It is the largest 
tendon in the body. 

670. Levers of the third class are 
the most numerous. The foot in rais- 
ing a weight upon the toes is an example. In nearly 
all joints of the arms and legs the power is furnished 
by the muscle attached to a bone near the fulcrum 
or joint, while the weight is farther away or near the 
outer extremity of the bone. Most of these muscles are 
so attached to their bones that they must exert a force 




Right forearm. 



MUSCLES 375 

greater than the weight which they move. But the outer 
end of a lever moves over a greater distance in a given 
time than the part near the fulcrum. So if a muscle 
loses power by its attachment to a bone, it gains in rapidity 
of motion. The muscles of the body are strong enough to 
combine strength with quickness of motion. 

The joints of the arms and legs are mostly so arranged that the limb 
can form a straight line, but can be bent in only one direction. The 
muscles which bend a limb are called the flexors^ while those which 
straighten it are called extensors. Flexor and extensor muscles are 
usually arranged in opposing pairs, with the flexors upon the front and 
the extensors upon the back side of the limb. The flexor of the elbow 
reaches from the elbow to the shoulder upon the front of the arm and 
is called the biceps. The extensor of the elbow extends in the same 
way upon the back of the arm and is called the triceps. Both the flexors 
and extensors of the wrist and fingers are situated between the elbow 
and the wrist. Only a few small ones are in the hand. 

The muscles which flex the knee end in strong tendons which can 
be felt as the hamstrings upon the back of the joint. The muscles 
which extend the knee end in a single large tendon inside of which is 
the patella. The patella acts as a pulley to protect the joint from the 
action of the tendon. 

The muscles of the ankles and toes are arranged much like those of 
the wrist and fingers. By practice while young, it is possible to learn 
to use the toes in the same way as the fingers. 

671. Back muscles. — The backbone is held upright and 
bent backward by large muscles which form ridges upon 
each side of the spine. They stretch the whole length of 
the spine so that the weight and power are at the same 
place while the fulcrum is the point of bending. Thus the 
spine is equivalent to a lever of the second or third class 
which uses most of the power of the muscle. So the back 
possesses great power with slow motion. 

672. Standing is done by the contraction of the opposing flexor 
and extensor muscles of the lower part of the body, so that the 



3/6 APPLIED PHYSIOLOGY 

spine and legs are held rigid. If one set overacts, it pulls the body to 
one side and tends to upset it. Then the opposing set contracts and 
rights the body. In standing, the two sets continually act in this way. 
. Walking is due to a regular action of the flexor and extensor muscles 
of the leg, in such a way that there is always one foot upon the ground. 
In running, the whole body is completely removed from the ground 
at every step. 

673. Face muscles. — The expression of the face is due 
to fiat muscles which are attached to the skin. A circular 
muscle surrounds the mouth and each eye, while other 
muscles radiate from their edges. The contractions of 





Illustration of the change of expression produced by the muscles 
of the mouth. 

these muscles cause the mouth and eyes to assume a great 
variety of positions. Even the nose may be moved by 
muscles, and in rare cases the ears also. The different 
shapes of the mouth and eyes which these muscles produce 
are reliable indications of the feelings of the mind. 

674. Muscular power. — The power which the muscles 
use is derived from the oxidation both of food and of their 
own substance. In their work they use about one fourth 
of the total heat produced in the body. 

A horse can drag about two thirds of its own weight, while an ant 
can drag 40 times its own weight, and a grasshopper can leap 300 times 
its own length. In proportion to their size, all insects seem to be far 
stronger than man. The strength of a muscle depends upon its thick- 



MUSCLES 377 

ness and not upon its length, yet in animals the muscle must be made 
many times longer than in insects as well as thicker. Thus the muscles 
of animals have more weight to lift and do a greater amount of work in 
proportion to their size. A man's muscle fiber is really the strongest 
known. An insect made as large as a man would probably be unable 
to move a limb. 

675. Precision of movement. — By means of the muscular 
sense it is possible to regulate the action of a muscle with 
great precision. But as the effort put forth is greater, the 
ability to regulate it is less. So while slow and delicate 
movements can be made with precision, rapid and power- 
ful motions are less under control. After a muscle has 
exerted itself to its full capacity, it is unable to perform 
delicate movements with precision for some time. 

676. Alcohol and muscle. — Strong drink in any form dimin- 
ishes both the strength and the endurance of muscles. Soldiers and 
athletes are not allowed to use it during periods of great exertion. It 
also interferes with the precision of movements. Drinkers are not 
allowed to work at railroading, where quickness and precision of move- 
ments are always required. Tobacco also weakens the muscles and 
lessens their precision of movement. 

677. Physical effects of exercise. — When used, most 
cells of the body take in more nourishment, and increase 
in size and strength. Muscles, especially, grow larger and 
stronger by use. Then the digestion, circulation, and 
respiration all show increased vigor to supply them with 
extra energy. Thus the whole body grows stronger. 

Round shoulders are most often due, not to weakness of the spine, 
but to weakness and inaction of the muscles of the back. The remedy 
is not to apply braces, for that only permits the muscles to rest and be- 
come weaker, but to make constant efforts to throw the shoulders back 
and so to increase the strength of the muscles. Military drill makes 
soldiers erect for this reason. 

678. Overwork. — If the muscles turn too much heat 
of the body to motion and work, there is too little left 



378 APPLIED PHYSIOLOGY 

to carry on the actions of the internal organs. Then 
there will be less food prepared for the repair of the cells, 
and to replenish the fuel for oxidation. So the whole 
body, including the brain, will remain fatigued. Besides 
the energy expended by the muscles, the brain also does a 
large amount of work in sending orders for their work. 
Probably the nervous system always becomes fatigued 
before the muscles. 

679. Kinds of exercise. — It is a problem for students 
and clerks to determine how much exercise will rest and 
stimulate the brain to the greatest degree, and yet take 
no energy from it. The kind which a person enjoys best 
is the best exercise for that person. If possible, the exer- 
cise should be of a form which will turn one's thoughts 
completely from the day's work and from the exercise 
itself. So a useful occupation or some absorbing game is 
especially valuable as exercise. Dumb bells, chest weights, 
and all kinds of gymnastic exercises are excellent for 
developing the muscles. Their only disadvantage is that 
their use becomes monotonous, and a person must force 
himself to use them. They have the advantage that they 
can be exactly regulated to develop any defective part of 
the body. When done in classes and under an instructor 
they are especially valuable. 

680. Amount of exercise. — A few moments of brisk 
running or romping will set the blood flowing faster and 
produce a clearer brain than an hour of slow walking. A 
person's own feelings should warn him when to stop. 
Boys and girls need plenty of exercise toward the end of 
their time of growth. A body well developed by exercise 
carries its strength through life. 

In a school, a position upon either the baseball or football or athletic 
team often uses the surplus energy which in former years was expended 



MUSCLES 379 

in midnight hazings, and also develops the traits of bravery, manliness, 
and self-reliance. There is a special danger of overexertion in com- 
petitive sports, but with intelligent oversight of the teachers they are a 
great benetit to all. 

SUMMARY 

1. Cells whose use is to produce motion are called 

muscle cells. 

2. In the arteries and in most of the organs of the chest 

and abdomen are spindle-shaped muscle cells, which 
are not affected by the will, but are controlled by 
the sympathetic system. 

3. Muscles covering the bones and moving the body 

under the control of the will form one half of the 
body. 

4. Voluntary muscles are made of ribbonlike cells which 

are marked crosswise. 

5. Impulses from motor nerves cause a muscle to be- 

come thicker and shorter, so that it moves any- 
thing attached to its end. 

6. A muscle ends in a stringlike tendon which crosses a 

joint, and is attached to the lower of the two bones 
which form the joint. 

7. Muscles are arranged in pairs. Those upon the back 

side of a limb usually straighten the joint, while 
those upon the front side bend it. 

8. Owing to the manner of their attachment, most muscles 

must put forth far greater force than the weight 
which they can lift. 

9. A piece of a man's muscle is stronger than any other 

muscle of the same size. 
10. The power for contraction of a muscle is derived from 
the heat of oxidation within the body. About one 
fourth of the heat is thus used. 



380 APPLIED PHYSIOLOGY 

11. By exercise of the muscles, the nutrition of the whole 

body is improved. 

12. Too much exercise uses the power which should go 

to the brain and other organs and so harms the 
body. 

13. That form of exercise is usually best which most 

interests a person. 

DEMONSTRATIONS 

165. Skin a chicken's leg and separate each muscle. Show their 
broad upper attachments and the small tendons into which the lower 
ends taper. Cut off the skin from the lower parts of the legs and toes 
and show how the tendons are attached to the toes. Notice that bend- 
ing the leg tightens the tendons and flexes the toes. Explain how this 
compels the toes to grasp the perch while the fowl is roosting. Pick a 
muscle apart to show the separate fibers. Sketch a muscle. 

166. Point out the main groups of muscles upon a boy. Have him 
perform such motions as raising his arm and clenching his fist, and feel 
what muscles are in action. Notice that when one set of muscles is in 
action the opposing set also acts so as to steady the limb. Point out 
the tendons, especially in the wrist and knee. 

167. With two needles tear apart a small shred of muscle from a 
piece of cooked meat and examine it under the microscope with a power 
of at least 200 diameters. Sketch the ribbonlike muscle cells and their 
fine cross markings. Notice the small amount of wavy connective 
tissue between the cells. Examine a prepared specimen to show the 
cells cut across and the capillaries surrounding the cells. 

168. Show involuntary muscle cells by preparing a shred from a 
fowPs gizzard, as in demonstration 167. Sketch the specimen. 

169. Hold a pencil firmly with the elbow flexed. Contract all the 
muscles of the arm strongly. Notice that the whole arm trembles. 
Now let the pencil tap the table by means of this trembling motion, and 
notice that the taps are about ten a second. Explain that the taps are 
due to successive motor impulses from the brain. Now tap the table 
rapidly with the ordinary motion of the hand. Notice that it can be 
done only about five or six times a second. Explain that in this case the 
mind must cause two separate sets of muscles to contract alternately. 



MUSCLES 381 

REVIEW TOPICS 

1. Show that motion is essential to the process of Ufe. 

2. Describe involuntary muscles and tell their use. 

3. Describe how voluntary muscles appear to the naked 

eye and under the microscope. 

4. Describe tendons; how they cross the joints; and 

their attachment to bones. 

5. Describe the contraction of a muscle. 

6. Describe the three kinds of levers ; show how bones 

and muscles form levers ; and give examples of each 
kind. 

7. Describe the arrangement of muscles in opposing sets. 

8. Describe the action of muscles at the elbow ; at the 

wrist ; at the fingers ; at the hip ; at the knee ; at 
the ankle ; at the toes ; in the back ; over the abdo- 
men ; and upon the face. 

9. Show how standing is performed ; how walking ; and 

how running. 
Give the source and amount of muscular power. 
Show that great exertion impairs the precision of 

movements. 
Show that muscle training is really mind training. 
Show that physical exercise benefits the whole body ; 

and that overwork fatigues the brain. 
Show what kind of exercise is the best. 
Show how to regulate the amount of exercise. 
Give an estimate of the value of competitive sports in 

schools. 



CHAPTER XL 
BACTERIA AND DISEASE 

681. Dangers to life. — Man's health is often assailed 
by his inward appetites and desires. He is also exposed 
to accidents and dangers from without. Formerly men 
were in constant danger from wild animals, but now man — 
the noblest and most powerful living being — is constantly 
assailed and often conquered by the smallest and simplest 
of living creatures. In the midst of his work he may be 
stricken with a deadly disease because millions of tiny 
creatures are poisoning the cells of his body. 

The microscope has revealed a world of tiny creatures of 
an infinite variety of form and manner of life. Three of 
the simplest forms are yeasty moldy and bacteria. All of 
them are of importance to man. 

682. Yeast is a plant which consists of a single cell 
scarcely larger than a red blood cell. The cells live upon 
sugar, and begin a series of changes to return it to the air 
and water for use as plant food. Were it not for this 
provision, much plant food might encumber the earth in 
the form of sugar and starch, and both man and animals 
might starve. After the sugar upon which yeast cells feed 
is used up, they remain in a dormant state, and some be- 
come dried and pass off as dust. Some are always float- 
ing about in the air ready to grow in anything containing 
sugar. Yeast must have warmth and moisture for its I 
growth. So cold or dried fruit does not sour. Yeast isj 

382 



BACTERIA AND DISEASE 



383 



used in bread making and in the manufacture of alcohol 
(see Chapter IV). 

683. Molds form a class of plants which may grow in 
nearly all kinds of moist substances, and there induce a 
kind of decay. They may usually be recognized by their 
furry growth on the surface of the affected substance. 




Diagram of mold (X 200). 

a ball of spores above the surface. 
b threads beneath the surface. 
c spores beneath the surface. 



The plants themselves are usually a series of threads which 
burrow beneath the surface. At intervals they send up 
slender shoots which bear germ cells or spores. These 
shoots constitute the fur which is usually called mold, but 
many kinds form their spores beneath the surface. The 
spores are microscopic in size, and can float in the air and 
grow into mold plants when they fall upon a suitable soil. 
Most forms grow only on dead material, but a few can 
grow on living matter. The smut and rust on grain and 
fruit are plants similar to molds. Ringworm is due to a 



384 APPLIED PHYSIOLOGY 

mold which grows in the human skin. Mildew ^nd toad- 
stools belong to the same family as molds. In nature 
molds disintegrate, and return to the soil and air all kinds 
of dead plant and animal substances, especially hard and 
resisting tissues like bones, tree trunks, and skins, so that 
they can again become available as plant food. In warm, 
humid weather molds grow readily and are often destruc- 
tive to food and clothing. 

684. Bacteria. — The smallest and simplest, as well as 
the most numerous of living creatures, are round or rod- 
shaped bodies from 2"5^o"o ^^ lo'io'o ^^ ^^ ^^^^ ^^ breadth, 
and seldom more than i-^-q-q of an inch in length. They 
are sometimes called ^nicrobes^ but more common names 
are bacteria or germs. They are all plants whose mode of 
growth somewhat resembles the yeasts and molds. Like 
yeast and mold they, or their spores, are scattered every- 
where in the air. When they fall upon moist albumin they 
grow. A single one can produce over 10,000,000 in the 
course of twenty-four hours. They often resist influences 
which would destroy most other forms of life. Even boiling 
for five minutes fails to destroy the spores of some. 

685. Effects of bacteria. — Bacteria destroy the substances 
in which they grow. Most forms of decay are due to the 
action of certain varieties of bacteria. They cause dead 
matter to become soft and melt away, usually with the 
production of foul-smelling gases and a variety of poison- 
ous ptomaines. In the soil there are forms of bacteria 
which oxidize all kinds of animal and vegetable albumin 
as thoroughly as though it were burned. Thus bacteria 
destroy the dead and waste matter of vegetables and ani- 
mals and prepare it for vegetable food again. Yeast, mold, 
and bacteria are indispensable friends of all living beings ; 
and decay is a step in the preparation of our food. 



BACTERIA AND DISEASE 



38S 




Bacteria growing in the mouth (x 400). 

The specimen was obtained by scraping a 

healthy mouth. 

a nucleus of an epithelial cell. 

b different forms of bacteria. 

c outline of an epithelial cell. 



686. Effects of bacteria upon living bodies. — Wherever 
there is a moist cavity containing albumin, bacteria may 
grow. The mouth is 
usually swarming with 
them, and may be offen- 
sive from the decay 
which they cause. They 
also grow abundantly in 
the intestine. A few 
forms can grow in the 
lymph spaces within a 
living body. Their poi- 
sons, circulating with the 
blood, may produce vari- 
ous diseases. Erysipe- 
las, diphtheria, typhoid 
fever, consumption, cholera, lockjaw, and the grippe are all 
caused by living germs which enter the circulation from 
without. Because these diseases are always caused by 

an influence from outside 



they are said to be infec- 
tious. 

Measles, scarlet fever, 
mumps, whooping cough, 
and smallpox also are due 
to some influence from 
without the body. This 
influence is supposed to 
proceed from a kind 
of germ, also. These 
diseases can be caught 
by being in the same 




Bacteria growing in a kidney and producing 
an abscess (x 300). 

a kidney tube. 

b white blood cell attacking bacteria. 

c bacteria. 

d blood tube of the kidney. 



room with a sick person, and so are said to be contagious. 

OV. PHYSIOL. — 25 



386 APPLIED PHYSIOLOGY 

687. How bacteria enter the body. — Germs of an infec- 
tious disease can grow outside the body in a damp soil 
containing animal or vegetable matter. They may grow- 
in damp clothing, or in sinks or wells, or in the soil, and 
may cause disease in whoever happens to take them into 
the body. Dirt and filth make good soil for the growth of 
the germs, and are well-known causes of disease. The 
germs may become dry and remain in a dormant state for 
years, and finally produce the disease again. 

Bacteria may enter the body wherever the epithelium is gone, and 
the lymph spaces are bare. Even a scratch or a pin prick may admit 
thousands at one time. They can also enter through the mucous mem- 
brane of the nose or throat, or they may be swallow^ed in drinking 
water or licked off from a knife or spoon which another person has used. 

688. How the body destroys bacteria. — Germs of disease 
constantly surround us, and the skin is constantly being 
scratched and pricked, affording them entrance. Yet only 
in rare instances do they grow and produce sickness, for 
the body has three very efficient weapons of defense. 

First. The white blood cells have a special power of 
seeking out bacteria and the toxins which they produce, 
and of enveloping and destroying them. A 

Second. The plasma of the blood and lymph, by some " 
chemical power, is able to destroy germs of disease. 

Third. The serum of the blood often contains a sub- 
stance called an antitoxin, which, while it may be a poison 
itself, also poisons the germs and so stops their action. 
When a disease has progressed for a few days or weeks, 
the antitoxin is formed in sufficient amount to poison the 
germs, and so the disease comes to an end. 

If the toxins of diphtheria germs grown outside the body are injected 
into a horse, the plasma of its blood will contain the antitoxin of the 
disease. If its blood is drawn and allowed to clot, the clear serum will 



BACTERIA AND DISEASE 387 

contain the antitoxin, and if injected into a man suffering with diphthe- 
ria, will tend to overcome the germs and to cure the disease. 

Cows sometimes have a disease which seems to be a modified form 
of smallpox. By vaccination, the same disease can be transmitted to a 
man in whom it causes but slight inconvenience, but yet protects him 
against smallpox almost as thoroughly as an attack of the disease it- 
self. Universal vaccination has destroyed the terrors of smallpox, so 
that from being one of the most common and deadly of diseases it is 
now one of the rarest. 

689. Destruction of germs outside the body. — The sun is 

one of the most efficient agents in destroying bacteria of disease. It 
acts partly by drying the food upon which they live and partly by 
means of its own chemical power. An abundance of sunshine in a 
place renders it almost surely free from disease. In some hot and dry 
climates decay is almost unknown, for bodies become dried before 
the germs can grow. On the other hand, darkness, decay, and disease 
go together. 

The w/;/<^ drives away the germs. In the open air it is almost im- 
possible to transmit disease. In closed rooms, germs which are given 
off from a diseased body may collect in great numbers, and in sick 
rooms may reenter the sick person and so prolong his sickness. Run- 
ning water also removes the germs. 

The soil destroys germs of disease. In it are special germs whose 
work is to oxidize all organic matter, including other kinds of germs. 
It also filters out the germs so that they can spread only a few feet, un- 
less the ground is continuously soaked with germ-laden sewage. 

690. Antiseptics. — Man uses three principal means to 
destroy disease germs which may threaten him. In the 
first place, he may wash them away with soap and water. 
He can thus get rid of most germs. 

Secondly. A boiling heat applied for fifteen minutes 
will kill all kinds of germs. A substance freed from 
germs is said to be sterilized. Clothes and utensils used 
in a sick room can be made safe for future use by boiling. 
Before a surgical operation, the instruments and dressings 
are thoroughly steriUzed by boiling. 



388 APPLIED PHYSIOLOGY 

Thirdly. A variety of chemical substances called anti- 
septics are poisonous to bacteria and destroy them almost 
at once. Carbolic acid added to from twenty to one hun- 
dred times its weight of water is very efficient in destroy- 
ing germs which it can touch. Bichloride of mercury 
added to from one thousand to five thousand times as 
much water, is also very good, but it destroys iron or tin 
vessels. Chloride of lime is also much used. 

Substances must come into intimate contact with germs in order to 
kill them. A little carbolic acid or other antiseptic may impart an 
odor to a room or overcome a smell, but to destroy the germs it must 
be applied in quantity directly to the germ. 

Before a surgical operation the surgeon washes and sterilizes his 
hands, and covers his clothes with a sterilized gown. He carefully 
avoids touching any object which has not been sterilized either by heat 
or by chemicals. Before he operates he scrubs and sterilizes the field 
of operation just as he did his hands, and then surrounds it with steril- 
ized towels. At the end of the operation he covers the wound with a 
dressing which has been sterihzed by heat or chemicals. Then no 
germs can enter, and the largest wounds heal in a few days without 
pain or discharge. The safety of operations now as compared with 
those of twenty years ago lies in the discovery of how to exclude germs 
of disease. 

691. Care of a sick room. — When a person is sick, every 
effort should be made to exclude germs of sickness. Fresh air and 
sunshine are always of the utmost importance in a sick room. It will 
always be better to run the risk of having the room a little cold than to 
have its air close. 

In contagious and infectious diseases, air and sunlight are the chief 
means of destroying the germs. 

Cleanliness should always be enforced in a sick room. The night 
clothes and bed linen should be changed as often as they are soiled. 
The whole body should be bathed daily, and the teeth and mouth 
cleansed. 

Talking above all things disturbs a patient. Especially avoid all 
references to doleful cases of suffering like the patient's. Do not ask 



BACTERIA AND DISEASE 389 

him if he will have this thing or that, but bring it to him without 
annoying him with the necessity of deciding for you. Do not argue 
with the patient, but kindly agree with him. Be good tempered and 
always thoughtful of his welfare. 

In a cojitagious disease all visitors should be excluded from the room, 
and all furniture not absolutely necessary should be removed. 

When the disease is at an end, the sick room should be thoroughly 
scrubbed with an antiseptic. It should be opened to the sunlight and 
air for several weeks before being used again. Everything possible in 
the room should be boiled or scrubbed. The patient should receive a 
thorough bath before leaving the sick room. 

692. Blood poisoning. — Disease germs may grow upon 
any open wound, making it tender and causing it to run 
matter. In severe forms they cause a swelling of the sur- 
rounding parts, producing erysipelas or blood poisoning. 
All this can be prevented or overcome by applying clean 
or antiseptic dressings. 

Milk, in summer time, forms a good soil in which germs 
from the air grow and form acids and other poisons. 
They produce stomach and intestinal disease in bottle-fed 
babies. Boiling the milk and bottles destroys the bacteria 
and prevents the disease. 

Consumption or tuberculosis, is the germ disease most 
to be feared. Its germs will grow in any tissue of the 
body and there produce tiny nodules like pinheads. After 
a while these nodules break down and form abscesses. 
They are found most (5ften in the lungs. 

The disease spreads mainly by means of the germs 
given off from the mouth. Becoming dried, they float in 
the air. So all secretions from the mouth should be col- 
lected and destroyed. 

693. Boards of health. — In every community the law estab- 
lishes boards of health, whose duty it is to see that cases of conta- 
gious diseases are properly isolated ; to see that no premises become 



390 APPLIED PHYSIOLOGY 

filthy, and that no diseases are brought into the country from foreign 
lands. Owing to the strictness and efficiency of these boards, conta- 
gious diseases are now as rare and harmless as they were once common 
and deadly. . 

SUMMARY 

1 . Yeast is composed of living plants which begin the work 

of returning sugar back to its original elements. 

2. Mold is composed of tiny rodlike plants which grow 

through animal and vegetable tissues and destroy 
their albumin. 

3. Bacteria are the smallest living beings. They cause 

decay and change albumin back to its elements in 
the air and soil. 

4. Bacteria may produce virulent poisons. 

5. A few kinds of bacteria grow in the body and there 

produce various forms of disease, some of which 
can be transmitted to other persons. 

6. The body is protected against the bacteria of disease 

by the white blood cells, by the plasma, and by sub- 
stances produced in the blood. 

7. Outside of the body, sunlight, fresh air, running water, 

and the soil destroy disease germs. 

8. Man destroys disease germs by washing them away, 

by boiling objects containing them, and by poison- 
ing them with such substances as carbolic acid and 
bichloride of mercury. 

9. Sunlight, fresh air, and cleanliness are essentials in 

every sick room, and especially in infectious diseases. 

10. After an infectious disease, the room and all its con- 

tents should be scrubbed, and thoroughly aired for 
a month. 

11. The law organizes boards of health to control infec- 

tious diseases and their causes. 



BACTERIA AND DISEASE 39; 



DEMONSTRATIONS 

170. Place a little yeast upon a microscope slide and examine it 
with a power of at least 200 diameters. Notice the oval cells from 
which smaller cells are budding. 

171. Take a bit of mold from cheese or bread and examine it with a 
power of at least 200 diameters. Notice the strings of mold which 
appear like very small jointed rods. Notice the collections of round 
spores at the tops of the projecting stalks. 

172. Place a little hay in a bottle of water and set it in the sun. 
After a few days, place a drop of the water upon a glass slide and 
examine it with a power of at least 400 diameters. Notice that 
numerous bodies of various sizes and shapes are swimming in the 
drop. These are the aniinalcidcB which older books describe. Notice 
also the real bacteria w-hich appear as the finest kinds of dots and short 
lines. Most of them are in constant motion. Only a few kinds of 
bacteria can be recognized by their appearance. 

173. Prepare some gelatine as if for the table, and pour some 
while hot into a tightly covered dish which has been boiled. Take off 
the cover for a moment before the class, and, replacing it, set the dish 
aside for a few days. Then a few specks of mold or of scum w ill appear 
upon the surface, each showing where a germ has fallen from the air 
and multiplied to form the spot. Explain that bacteria are studied in 
laboratories in much the same way. 

174. Have a druggist prepare a solution of carbolic acid i to 100, 
and of bichloride of mercury i to 1000. Show the class how they should 
be used in washing the hands and clothes. Also show^ the pure drugs, 
and warn the class against using them in this form. Show also chloride 
of lime and other common antiseptics. 



REVIEW TOPICS 

1. Describe yeast and give its uses in nature. 

2. Describe mold and give its uses. 

3. Describe bacteria and their relation to decay. 

4. Give the uses of decay. 

5. Show how bacteria can enter the body and how they 

produce sickness. 



392 APPLIED PHYSIOLOGY 

6. Show how bacteria are destroyed in the body by white 

blood cells and by the blood plasma. 

7. Describe an antitoxin and tell how it is used in treat- 

ing diphtheria. 

8. Describe vaccination. 

9. Show how bacteria are destroyed by sunlight ; by the 

air ; by running water ; and by the soil. 

10. Show how man destroys bacteria by cleanliness ; by 

heat ; and by antiseptics. 

11. Show how a surgeon destroys germs before and after 

a surgical operation. 

12. Give some hints about the care of a sick room; and 

about cleansing it after an infectious disease. 

13. Describe the disease tuberculosis, or consumption. 

14. Give the duties of a board of health. 

Note. — For a more extended discussion of bacteria and disease, see "The 
Story of the Bacteria," by T. Mitchell Prudden, M.D. 



CHAPTER XLI 

REPAIR OF INJURIES 

694. Injuries. — Many causes outside the body operate 
upon its cells to injure them. Excessive heat or cold may 
impair their vitaHty or cause their death. A sudden change 
from heat to cold is a common cause of injury. Blows and 
cuts may kill whole armies of cells. Above all, bacteria 
may cause injury and disease. In a few hours, the injured 
part shows a change, which is apparently due to an in- 
crease of the injury, but which is really caused by nature's 
attempt to repair the part. 

695. Congestion. — After an injury has been received 
the first step in its repair is to dilate the arteries so as 
to permit more blood to flow through the part. Then 
more plasma will penetrate into the lymph spaces. This 
produces redness and some swelling and is called conges- 
tion. Congestion is a sign of attempted repair. This 
alone may be sufficient to heal the injured part. 

696. Inflammation. — If the injury is greater, there is 
a change in the behavior of the white blood cells. Ordi- 
narily they tend to flow more in the outer part of the 
blood stream, but when the arteries enlarge as a result of 
injury they adhere to the sides of the smallest blood tubes 
and some pass entirely through their walls and lodge in the 
lymph spaces. There they envelop and digest the injured 
parts and carry them away with the lymph. The lymph 
and blood cells have great power of absorbing blood and 

393 



394 



APPLIED PHYSIOLOGY 



dead cells, or even such substances as stitches left in the 
body by a surgeon. The excess of white blood cells causes 
more swelling, and some pain. This is an aggravated form of 
congestion, and is called inflammation. Some of the white 
^^ blood cells grow in place 

a 



)»->, 




^^ 

Beginning of inflammation (x 400). 

a white blood cells adhering to the wall of a 
capillary and passing through it, 

b white blood cells which have passed outside 
of the capillary in order to repair an 
injury. 

c red blood cells passing through the capil- 
lary. 

d wall of capillary. 



of the removed cells and 
so fill in the gap. Each 
cell becomes long and 
branched and finally de- 
velops into a connective 
tissue cell. If the new 
cells are in great amount, 
they have a different ap- 
pearance from the origi- 
nal cells and are then 
called a scar. 

697. Repair of cuts. — 
When a cut is made in 
a tissue, the same proc- 
ess takes place, but in addition new blood tubes sprout 
from each side of the wound and interlace in the middle. 
The white blood cells grow about the new tubes and 
become connective tissue and so bind the edges of the 
cut together. 

When the skin is injured, the white blood cells form 
new tissue upon the surface while the epithelium spreads 
over it from the edges, stopping the growth and complet- 
ing the healing process. Sometimes the new connective 
tissue grows faster than the epithelium and forms soft 
tufts, which project above the healthy flesh. These tufts 
are 0.2^^^^ proud flesh. If they are scraped off, or cauter- 
ized, the epithelium is enabled to cover the wound, and 
to complete the healing. 



REPAIR OF INJURIES 



395 



698. Injuries due to bacteria. — If bacteria cause the 
injury to the cells or if they enter and grow after the 
injury is done, the blood cells must fight them as well as 
repair the damage. Sometimes they cannot do both at 
once. Then the white blood cells and plasma leave the 
blood tubes to a still greater degree and lay siege to the 
bacteria until they 
completely fill the 
lymph spaces. They 
even stop up the 
blood tubes, produc- 
ing great swelling 
and pain. White 
blood cells and bac- 
teria are now tightly 
wedged among the 
injured tissues with 
no chance for escape 
and with no nourish- 
ment. Then the 
whole injured part 
becomes soft and 
finally bursts and 




The repair of a wound (x 200). 



a new white blood cells upon the surface of a raw 

spot. 
d growing white blood cells. 
c new capillary. 
d new branch from a capillary. 
e older white blood cells which are becoming 

elongated and branched like connective tissue 

cells. 

runs out as a creamy / old capillary sending out a new branch. 
, , n J i ^ old connective tissue. 

matter called pi^s. ^ 

Thus nature sacrifices a part of the body in order to get 
rid of the bacteria which threaten to overcome the whole 
body. Then the white blood cells grow and repair the 
wound as in clean wounds. A mass of pus in the body is 
called an abscess. Every abscess or collection of pus is 
caused by bacteria. 

If bacteria grow upon an open cut, the white blood cells must devote 
part of their energies to fighting them, and so healing goes on slowly, 



396 



APPLIED PHYSIOLOGY 



while the dead cells, or pus and plasma, run off in a continuous stream. 
So bacteria hinder the repair of wounds, and prevent their edges from 
growing together directly. Then the cut must slowly heal from its 
bottom. When a wound begins to be tender and to discharge, it is 
said that one has taken cold in it. Taking cold in a wound means 
that bacteria are growing in it. Their toxins may poison the whole 
body and produce a severe fever, which may cause death. Surgeons 
now exclude bacteria from the wounds which they make. The white 
blood cells then have nothing to do but repair the cut, and every part 
of the wound heals at once. Healing applications do good mainly by 
destroying geims whicL may come near the wound. 

699. Treatment of in- 
flamed wounds. — A 

tender discharging 
wound should be 
cleanec with boiled 
water, and covered with 
a clean antiseptic dress- 
ing, to soak up the dis- 
charges and bacteria. 
The dressings should 
be changed as soon as 
they become full of 
matter. In this way 

the germs will be removed, and the white blood cells will 

grow unhindered. 

When an abscess is forming, the heat of a poultice dilates the blood 
vessels, and so hastens the softening process. Thus it "brings the 
abscess to a head" and hastens the discharge of the pus. Since the pus 
will form anyhow, it is always better to open the abscess and let out 
the matter at once. This can be done without pain by using cocaine. 




The second stage of inflammation ( x 200) . 

a white blood cells which have left the capillary. 
b white blood cells which nearly block the 

capillary. 
c a few red blood cells which still circulate. 
d wall of the capillary. 



700. Taking cold upon the lungs. — When a mucous 
membrane is injured, as by exposure to cold, there will 
be the same changes in its blood tubes as in a wound 



REPAIR OF INJURIES 



397 



of the flesh. Then the membrane will be red and tender 
and possibly swollen. Owing to the thinness of the mem- 
brane and of its epithelium, the plasma and white blood 
cells will come to the surface. The matter may collect 
until it is coughed up and expelled. The nose and throat 
are the most often affected, but in severe cases it extends 
to the trachea and lungs. When the matter fills the air 
sacs of a part of the lung, the disease is called pneumonia. 







The third stage oi inilammatioii, or the formation of an abscess ( X 50) . 

a epithelium of the skin softened and bursting. 

b white blood cells which have packed the tissues full and shut out nourishment. 

c blood tube stopped by white blood cells. 



In order to take cold there must be an injury to the cells, and 
bacteria must grow upon the injured spot. It often happens that the 
cells are exposed to injury, and no cold is contracted, for germs do 
not happen to grow, while on the other hand the exposure may be 
slight, and yet may enable germs to produce a severe cold. 

In colds and in an abscess, the pus and discharged substances are 
not foul matters which are circulating in the blood, and which should 
be expelled, but consist of the strong blood cells which have died 
fighting for the defense of the body, and of plasma, which is an efficient 
protection against the germs. Both being dead and charged with the 
toxins of the bacteria, they should be expelled from the body. 



398 APPLIED PHYSIOLOGY 

When a cold is first coming on, a hot bath and hot drinks and hot 
bed clothing, together with a liver stimulant, may cause the skin and 
liver to excrete enough toxins to enable the white blood cells to over- 
come the bacteria. 

701. A long life. — Although in former times man was 
often conquered by bacteria of disease and even now is 
continually assailed, yet now he knows more about his tiny 
foes and is able to protect himself. He knows that his 
eating, his breathing, his work, his rest, and in fact his 
every action will render his cells either more or less able 
to combat with disease germs. If all men would live up 
to their knowledge, germs of disease would find no lodg- 
ment in the body, while there would be no cause of dis- 
ease in the body itself. Then man's mind would remain 
with his body far beyond the allotted three score and ten 
years, and, during all its long stay, would find the body a 
willing servant to build the ideal plans of the spirit into 
enduring realities. 



SUMMARY 

1. An injury to the cells of the body causes the arteries to 

dilate and bring more blood to the part. 

2. Over a sore spot the white blood cells form new con- 

nective tissue while the epithelium of the healthy 
skin spreads over the new tissue, stopping its growth 
and completing the healing process. 

3. When bacteria are growing in an injured spot, the white 

blood cells attack them, but are often killed them- 
selves and pass off as creamy matter called pus. 

4. If the white blood cells cannot overcome the bacteria, 

they hem them in until they and the tissues starve 
and run out as pus. 



REPAIR OF INJURIES 399 

5. The changes which take place about an injured part 

cause it to become red, painful, swollen, and warmer 
than usual. 

6. If wounds and all other injuries were protected against 

bacteria, they would heal at once without discharg- 
ing pus or other matter. 

7. In injuries to mucous membranes, the white blood cells 

and plasma pass through the thin tissues to the sur- 
face and are discharged at once. 

8. Taking cold means an injury due to bacteria. 

9. The matter discharged from an abscess or from a 

"cold" is composed of the best cells of the body 
which have died in its defense. 



DEMONSTRATIONS 

175. Scratch the skin upon the lower part of the arm. Notice that a 
red line develops in a moment. Explain that the scratch injured the 
cells and partly paralyzed the blood vessels, and that the redness is due 
to more blood in the part, which has come to repair the damage and to 
protect the rest of the body. 

176. A pimple upon the face will illustrate the different stages of 
inflammation. Explain that a pimple may be caused by a prick too small 
to be noticed, but which has introduced some bacteria beneath the skin. 
Explain that the redness is due to the blood which has come to repair 
the damage Explain that the white spot upon the top of the pimple is 
the softened area through which bacteria and dead cells will finally pass 
out, and that the pus is composed of white blood cells which have died 
fighting to protect the body against the bacteria. 

177. Place a tiny drop of matter pressed from a pimple or a cut or a 
scratch upon a microscope slide and examine it with a power of 400 
diameters. Notice that it is composed of white blood cells, containing 
nuclei. Examine also a drop of mucus from the nose and notice that it 
consists largely of the same kind of cells. 

178. Obtain a prepared microscopic specimen from a wound in the 
process of healmg. Show that the newly formed tissue consists of 



400 APPLIED PHYSIOLOGY 

round blood cells upon its surface, and that in the deeper layers the 
cells grow larger and become branched. Explain that the deeper layers 
are the older and that their cells are white blood cells which are grow- 
ing to become connective tissue. 



REVIEW TOPICS 

1. Explain in order what happens in an injured part of 

the body, describing the increased flow of blood, 
and the action of the white blood cells. 

2. Explain the healing of a cut. 

3. Explain how a raw spot of skin becomes healed, and 

what part the epithelium takes in the process. 

4. Explain how bacteria in an injured part retard healing. 

5. Explain how white blood cells overcome the bacteria. 

6. Explain the formation of an abscess. 

7. Explain taking cold in a wound, and in a mucous 

membrane. 

8. Give the signs of inflammation and its use. 

9. Tell what composes the matter discharged from an 

abscess and from the nose and throat during a cold. 

10. Show how to treat a wound in which one has taken 

cold. 

11. Explain how to treat a cold of the air passages. 



GLOSSARY. 

Ab-do'men (Lat. abdomen, belly), the cavity of the body which contains 
the stomach, intestine, liver, pancreas, and spleen. 

Ab'scess (Lat. abs, away, and cedere, to move), a collection of dead 
creamy matter in the flesh of a living person. 

Ab-sorp'tion (Lat. ab, away, and sorbere, to soak in), taking a substance 
into the tissues of the body, without change in its composition. 

Ac-com-mo-da'tion (Lat. ad, to, co?i, with, and inodns, measure), adjust- 
ing the lens of the eye to the proper shape to cause the image of an 
object to fall upon the retina. 

A'cid (Lat. acere, to sour), any sour, irritating substance, which will 
corrode other substances. 

A'con-ite (Gr. akoniton, the plant commonly called monkshood), an 
extremely poisonous plant. It is used to lower fevers. In over- 
doses it produces extreme weakness of the whole body. 

Ad'e-noid vegetations (Gr. aden, gland, and eidos, form), collections of 
soft, grape-like bodies growing in the upper part of the pharynx. 
They are common in children. 

A-dul'ter-ate (Lat. ad, to, and alter, another), to make impure by an 
admixture of an inferior substance. 

Al-bu'min (Lat. albus, white, because it generally turns white when 
heated), a term applied to a class of substances, some form of which 
is the essential part of every living cell. It is composed of the 
elements carbon, hydrogen, nitrogen, oxygen, and sulphur. The 
form of albumin which is found in the white of an Qgg is spelled 
albiDiien. 

Al'co-hol (Ar. al-kohl, a powder of antimony used in painting the 
eyebrows), on account of its extreme fineness the name came to be 
applied to the product formed by repeatedly distilling wine, for this 
was supposed to be the real " spirits ^' of the wine. 

ov. PHYSIOL. — 26 401 



402 GLOSSARY 

Al-i-men'ta-ry (Lat. alere, to feed), having nourishing qualities capable 
of being used as a food, or pertaining to food. 

Al'ka-li (Ar. al, the, and kali^ a plant whose ashes were used in making 
glass), a substance whose properties are in contrast with those of 
an acid. An alkali forms soap when united with an oil. 

Al'ka-loid (Ar. alkali, and eidos, form), the substance in certain vege- 
table drugs which gives the drugs their characteristic qualities. A 
small dose of an alkaloid produces the same effect as a large dose 
of the drug from which it is derived. 

A-me'ba (Gr. amoibe, change), the simplest form of animal life, con- 
sisting of a single lump of jelly, capable of changing its shape at will. 

Am-y-lop'sin (Gr. amulojt, starch), the ferment in the pancreatic 
juice which changes starch to glucose. 

A-nat'o-my (Gr, ana, up, and te^nnein, to cut), the science which tells 
of the structure of living bodies. 

An-e'mia (Gr. a, without, and haima, blood), the state of the blood in 
which there are too few red blood cells and too httle plasma. 

An-es-the'si-a (Gr. a?i, not, and aisthanesthai, to perceive), a tempo- 
rary lack of sensibility produced by drugs. 

An'ti-dote (Gr. «;///, against, and didonai, to give), a substance which 
prevents a poison from acting upon the cells when it is introduced 
into the body. 

An-ti-sep'tic (Gr. anti, against, and sepein, to rot), a substance which 
prevents the growth of bacteria, and hence prevents rotting. 

An-ti-tox'in (Gr. aitti, against, and toxikon, poison), a substance which 
is produced in the body to overcome the poison of a disease. It is 
commonly applied to a substance used in the treatment of diphtheria. 

An'trum (Gr. ajttron, a cave), the hollow cavity within the upper jaw 
bone. 

A-or'ta (Gr. aeirem, to lift up), the large artery which rises from the 
left side of the heart, and distributes blood to all parts of the body. 

Ap-0-plex'y (Gr. apo, from, and plesseift, to strike), a sudden loss of 
consciousness, usually due to pressure upon the brain caused by a 
burst artery. 

Ap-pen-di-ci'tis, inflammation of the vermiform appendix. 

Ap'pe-tite (Lat. ad, to, 2in6. petere, to seek or long for), a strong desire 
for something. It is used mainly of the desire for eating and drinking. 

A'que-ous hu'mor (Lat. aqua, water, and humor, a liquid), the hquid 
which fills the eyeball in front of the lens. 



GLOSSARY 403 

Ar'gon (Gr. <2, not, and ergon, work), a gas (discovered in 1894) which 
forms about one per cent of the air. It resembles nitrogen. 

Ar'sen-ic (Gr. arsenikoft), a gray metal whose combinations with oxy- 
gen are very poisonous. 

Ar'ter-y (Gr. aer, air. and terein, to hold), the tubes which conduct 
blood to the cells of the body. After death they are empty, and it 
was formerly supposed that in life they contained only air. 

As-phyx'i-a (Gr. a, not, and sphuzein, to throb), death by suffocation. 

As-sim-i-la'tion (Lat. ad, to. and shnilis, like), the process of chang- 
ing digested food to substances like those which compose the body. 

A-stig'ma-tism (Gr. a, not, and stig?na, a point), the condition of an 
eye in which one part of the rays are brought to a focus sooner than 
another part. 

Au'ri-cle (Lat. amis, an ear), the upper two cavities of the heart. 
They are thin and resemble dog's ears. 

Bac-te'ri-um (pi. bacteria) (Gr. bacterion a staff), the simplest and 

smallest form of plant life, consisting of a tiny sphere or rod. Some 

kinds can grow in the human body and produce disease. 
Bel-la-don'na (Ital. bella, beautiful, and do7ina, lady), an herb which 

produces excitement of the brain and great weakness. It enlarges 

the pupils of the eyes, and was formerly used by ladies to render 

themselves more beautiful. 
Bi'ceps (Lat. bis, twice, and caput, head), the muscle upon the front of 

the upper arm which bends the elbow. Its upper end has two 

branches. 
Bi-chlo'ride of mer'cu-ry, a compound of mercury and chlorine. It 

is very poisonous especially to bacteria of disease. When dissolved 

in water in the proportions of one part to five thousand, it kills 

disease germs. 
Bi-cus'pid (Lat. bis, twice, and cuspis, a point), the' fourth and fifth 

teeth from the middle upon each side of each jaw ; each bicuspid 

ends in two points. 
Bile (Lat. bilis^, a yellow, bitter fluid formed by the liver cells and 

poured into the intestine. It is a part of the waste of the body, 

but while it is being excreted it assists the pancreatic juice and 

intestine in performing their w^ork. 
Bil-i-ru'bin (Lat. bilis, bile, and ruber, red), the coloring matter of 

the bile. It consists of broken down hemoglobin. 



404 GLOSSARY 

Blad'der, a thin muscular bag in which a fluid is stored in the body 
It is especially applied to the bag in the pelvis containing urine. 

Brain, the mass of nerve cells and nerve fibers which is inclosed with- 
in the skull. It is the seat of the consciously acting mind. 

Bright's disease, almost any disease of the kidneys. Dr. Bright 
gave the first true description of kidney diseases. He died in 
1858. 

Bron'chus (Gr. brogchos, the windpipe), one of the numerous branches 
into which the trachea divides. It is applied to the smallest sub- 
divisions as well as to the two main branches. 

Bunion, a swelling of the great toe joint caused by tight shoes. 

But'ter-ine, artificial butter made from butter and suet. 

Cae'cum (Lat. caecus, blind) ^ the blind or closed end of the large 
intestine ; the small intestine opens into the side of large intestine 
about an inch from its end. 

Caf-fe-ine {ka-fe'in)^ a white, bitter alkaloid obtained from coffee. 

Callus (Lat. callus)^ hard and thickened epidermis. It is caused by 
rubbing a part during hard work, and is nature's way of protecting 
the deeper parts from injury. 

Can-cellous (Lat. cancelli, a lattice), having an open or porous struc- 
ture. 

Cap'il-la-ry (Lat. capillus^ a hair), a hair-like blood tube. Capillaries 
surround each cell of the body. From them plasma and oxygen, 
go out from the blood to nourish the cells. ■ 

Car-bollc acid (Lat. carbo, coal, and olei(??t, oil), a poisonous sub- 
stance obtained from coal tar. It is commonly used to kill dis- 
ease germs and to prevent decay. 

Car'bon (Lat. carbo, coal), a substance, of which the diamond is the 
pure crystallized form. Coal, charcoal, and lampblack are more 
common forms. Combined with other substances it is a part of 
the bodies of all animals and plants. 

Car-bon'ic acid gas, a heavy, colorless gas formed when carbon burns. 

Car'di-ac (Gr. kardia, heart), pertaining to the heart. It is also 
appUed to the left end of the stomach, which lies just under the 
heart. 

Car'pal bones (Gr, karpos^ wrist), the bones of the wrist. 

Car'ti-lage (Lat. cartilago), the soft substance commonly called gristle 
which covers the ends of bones within joints 



GLOSSARY 405 

Casein {ka'se-in) (Lat. caseus, cheese), the part of the albumin of 
milk which forms the curd or clabber. In cow's milk nearly all 
the albumin is casein. The remaining albumin coagulates and 
forms a scum when the milk is heated. 

Cat'a-ract (Gr. kata, down, and rhegniaiau to break), a cloudiness of 
the lens of the eye which shuts out the light. 

Catarrh {katar') (Gr. kata, down, and rhein, to flow), an excessive 
production of mucus from the nose and throat. 

Cells (Lat. cella, a cavity), the smallest particles of the body capable of 
fulfilling the tests of life. 

Cellu-lose (Lat. cellula, a little cell), a substance which forms most of 
the framework of vegetable tissues. 

Ce-ment' (Lat. cae;fientu;;i, a builder's stone), the soft bone-like sub- 
stance which fixes the teeth in their sockets in the jaws. 

Cer-e-bel'lum (Lat. cerebellum, little brain), the rounded part of the 
brain situated under the cerebrum and above the medulla. It 
assists the brain to direct precise movements, as movements in 
which the body is balanced. 

Cer'e-bnim (Lat. cerebrum, brain), the uppermost part of the brain. 
In man it covers all the rest. It is the seat of consciousness and 
of thought. It receives all sensations, and sends all voluntary im- 
pulses to produce motion. 

Chem'is-try, the science of the composition of substances. It is 
concerned in destroying or decomposing substances, and in form- 
ing new substances having different properties from the original 
substances. 

Chlo'ral {klo'ral), a substance made from chlorine and alcohol znA used 
to produce sleep. 

Chlo'ride {klo'ride), a combination of the gas chlorine with another 
substance. Chloride of lime is used to kill disease gernis. Chlo- 
ride of sodium is common salt. 

Chlo'ro-form, a volatile liquid made from chlorine Tind for jny I. When 
its vapor is inhaled for some minutes it produces a deep sleep and 
complete insensibility to pain. When its inhalation is stopped, 
consciousness soon returns. It is used in surgical operations. 

Chlo'ro-phyll (Gr. chloros, green, and phullon, leaf), the green coloring 
matter of leaves. It forms starch out of carbonic acid and water. 

Chol'e-ra (Gr. chole, bile), a contagious disease of the intestine in which 
there is great pain, and an increased excretion and peristalsis. 



406 GLOSSARY 

Cho'roid (Gr. chorion^ skin, and eidos, form), the middle lining of the 
eye. It carries the blood vessels for the nourishment of the inner 
parts of the eye. 

Chyle {kile) (Gr. chulos, juice), the liquid produced by intestinal di- 
gestion. 

Chyme {ki7ne) (Gr. chiimos, juice), the partly digested contents of 
the stomach as they enter the intestine. The word is falling into 
disuse. 

Cilia {sU'i-d) (Lat. cilia, eyelashes), microscopic hairs upon the surface 
of certain cells. They are in constant motion to sweep out secre- 
tions and dust. They line the trachea and bronchi. 

Clab'ber, or bonny-clabber (Irish baine, milk, and clabar, mud), sour 
and curdled milk. 

Clav'i-cle (Lat. clavis, a key), the slender bone which extends from the 
breast bone to the shoulder. The collar bone. 

Co-ag-u-la'tion (Lat. coft, together, and agere, to force), the process 
of changing a liquid to a solid form of a different nature from the 
original liquid. Thus in curdled milk coagulation has taken 
place. 

Cocaine (ko'ca-in), a bitter, white substance obtained from coca. It 
benumbs pain when applied to the nerves and produces excitement 
of the brain. 

Coccyx {kok'six) (Gr. kokkux, a cuckoo), the small bone which forms 
the lower end of the backbone. It is shaped somewhat like a 
cuckoo's bill. 

Cochlea {kok'le-d) (Lat. cochlea, snail shell), the coiled canal of the 
inner ear in which the nerves of hearing end. 

Cold, an unhealthy state of a part of the body caused by exposure to 
coldness and dampness. It is an increased activity of the cells and 
an increased blood supply due to nature's attempt to repair the 
injury caused by the exposure. The injury is usually due ta the 
growth of disease germs. 

Colon (Gr. kolon), the large intestine. 

Con-ges'tion (Lat. con, together, and gerere, to bring), overfullness of 
the blood tubes of a part of the body. It is the first stage of repair 
of wounds and of inflammation, and is nature's way of supplying an 
excess of nutrition to repair an injured spot. 

Con-junc-ti'va (Lat. conjunctiviis, joined together), the mucous mem- 
brane lining the eyelids and covering the front of the eyeball. 



GLOSSARY 407 

Connective tissue, the stringlike cells scattered through the whole 

body to keep the other cells of the body in place. 
Conservation of energy, the law that no force is destroyed, but can be 

recovered as heat, electricity, motion, or in other forms. 
Contagious disease {kon-ta'jus) (Lat. contagio, a touch), a disease 

which can be transmitted through the air. 
Con-trac'tion (Lat. con, together, and trahere. to draw), the shortening 

and thickening of a muscle to produce movement in a part of the 

body. 
Cook (Lat. coquere), to prepare food by the use of heat. 
Cor'ne-a (Lat. corneus, horny), the round, bulging window in the front 

of the eyeball through which light enters the eye. 
Cor'pus-cle (Lat. corpuscuhutT, a little body), one of the cells which float 

in the plasma of the blood. 
Cra'ni-al (Gr. kr anion, skull), pertaining to the contents of the skull 

or brain. 
Cricoid cartilage {kri'koid) (Gr. krikos, a ring, and eidos, form), the 

ring which forms the lower part of the larynx. 
Cud, the food which most cloven-hoofed animals bring up from the 

stomach to chew the second time. 
Cu'ti-cle (Lat. cuticiila, little skin), the outer and insensitive layer of 

skin. The epidermis. 
Cu'tis (Lat. cutis, skin). A more common name is the derma. 

Deg'lu-ti'tion (Lat. de, from, 2in6. glut ire, to swallow), swallowing. 

De-lir'i-um (Lat. delirare, to rave), a state of mind in which judgment 
and reason are disordered and illusions of the senses are present. 
It is usually caused by fevers. 

Delirium tre'mens, a form of delirium which occurs in drunkards. It 
causes the sufferer to struggle violently to escape the torments of his 
imagination. 

Der'ma (Gr. derma, skin), the true skin, or the part beneath its insen- 
sitive covering. 

Di'a-phragm (Gr. dia. through, and phragnunai, to fence), the muscu- 
lar partition extending across the cavity of the body and dividing 
the chest from the abdomen. It is the main muscle of breathing. 

Diastole {di-as' to-le) (Gr. dia, through, and stellein, to place), the 
relaxation of the heart during which it is being tilled with blood in 
preparation for another beat. 



408 GLOSSARY 

Diffusion (Lat. diffusid), the act of passing through membranes appar- 
ently impervious. Thus, peptone passes by diffusion through the sides 
of the blood tubes in the walls of the intestine, and reaches the blood. 

Di-ges'tion (Lat. dis^ apart, and gerere, to carry or wear), changing food 
into such forms that it can pass through the walls of the blood 
tubes and become a part of the blood. 

Diph-the'ri-a (Gr. diphthera, leather), an infectious disease in which 
there is a skin-like membrane covering the affected part, usually the 
throat. 

Dis-lo-ca'tion (Lat. dis, apart, and locare, to locate), the separation of 
two bones whose union forms a joint. 

Dis-til-la'tion (Lat. de^ from, and stillare, to drop), the process of sepa- 
rating a substance which easily becomes a vapor from one which 
forms a vapor less easily. Heat is applied to the substance, and 
the vapor is cooled or condeiised to a liquid in a coil of tube from 
which it runs in drops, and hence the name. As far back as the 
year 1200 the process was used by the Arabs in their endeavors to 
find an essential spiritual principle which would sustain life and 
restore youth. 

Drop'sy, a uniform swelling of a part without pain or redness. It is 
an accumulation of lymph due to a disturbance in the circulation of 
the blood. 

Duct (Lat. duce?'e, to lead), any tube which conducts a secretion away 
from a gland. 

Du-0-de'num (Lat. dicodeni, twelve), the beginning of the small intes- 
tine for the length of about twelve finger breadths. 

Du'ra ma'ter (Lat. dura, harsh, and mater ^ mother), the periosteum 
lining the skull. It is very thick and sends prolongations into the 
main fissures of the brain to hold the brain in place. 

Dys-pep'si-a (Gr. dus^ ill, and peptein, to cook or digest), imperfect 
digestion of the food. 

E-mursion (Lat. e. out, and midgere^ to milk), a milky-looking liquid 

consisting of microscopic drops of oil floating in a liquid. 
En-am' el, the hard calcified tissue which covers the exposed parts of 

the teeth. 
En'er-gy (Gr. en^ in, and ergon, work), any force which can be made 

to do work. The energy of the body can be traced to oxidation 

within the cells. 



GLOSSARY 409 

Ep'i-der'mis (Gr. epi^ upon, and der?fta, skin), the thin insensitive 
layer of cells upon the outside of the skin. It is sometimes called 
the cuticle. 

Ep-i-glot'tis (Gr. epi, upon. diXid glotta, the tongue), the leaf-like lid upon 
the back of the tongue which closes the larynx when swallowing. 

Ep'i-lep-sy (Gr. epilepsis, a seizure), a disease in which, at intervals 
a person suddenly falls to the ground unconscious, while all the 
muscles of the body contract strongly. 

Ep-i-the'lium (Gr. epi^ upon, and thele^ nipple), the cells which cover 
the skin and mucous membrane and line the tubes of glands. Epi- 
thelium is a protection for the body, and does all the work of secre- 
tion and absorption. 

Er-y-sip'e-las (Gr. eruthros, red, and pella, skin), a disease of the 
skin in which there is pain, redness, and swelling. It is caused by 
the growth of bacteria of disease in a wound. It varies in severity 
from a simple maturated scratch to a severe blood poison. 

E-soph'a-gus or oe-soph'a-gus (Gr. oiso, I shall carry, and phagein, to 
eat), the tube connecting the mouth with the stomach. 

E'ther (Gr. aitkein, to burn), a colorless liquid which evaporates with 
such great rapidity that its vapor may catch fire if near a lamp. It 
is used to dissolve gums, and also, like chloroform, to produce in- 
sensibility during surgical operations. 

E'ther (Lat. aether, the upper pure air where the gods abode, in dis- 
tinction from the lower or true air in which man lived), the sub- 
stance which is supposed to pervade all space, and whose vibrations 
are supposed to form light, heat, and electricity. 

Eustachian tube {yu-sta'ki-an^, the tube leading from the middle ear 
to the pharynx. It is named after its discoverer, Eustachi, an 
Italian physician, who died in 1574. 

Ex-cre'tion (Lat. ex, out. and cretus, sifted), a waste substance extracted 
from the blood by the epithelium of a gland. 

Ex-pi-ra'tion (Lat. ex, out, and spirare, to breathe), breathing out air 
from the lungs. 

Ex-ten'sor muscles (Lat. ex, out, and tender e, to stretch), the muscles 
which straighten limbs. 

Fat, a white greasy substance composed of carbon, hydrogen, and 

oxygen, but with much less oxygen than is in starch. 
Fe'mur (Lat./^wwr), the thigh bone. 



41 GLOSSARY 

Fer'ment (Lat. fervimentum, boiling), a substance a small amount of 

which produces a chemical change in a large amount of another 

substance without losing its own identity or characteristics. During 

the process the most common ferment — yeast — liberates bubbles 

of gas, like a boiling. 
Fe'ver {hsit.febris, a fever), increased warmth of the body due to poisons 

of disease. 
Fi'brin {1.2it. fibra, a thread), the stringy threads of coagulated blood 

albumin which permeate the blood and imprison its cells and plasma, 

causing it to become jellylike or clotted. 
Fib'u-la {hdit. fibula, clasp), the long bone upon the outside of the shin 

bone. 
Fil-tra'tion (Lat. feltrum, felt), separating a solid from a liquid by 

straining it through a porous substance. 
Fis'sure (Lat. fissura, a cleft), one of the deep furrows upon the sur- 
face of the brain. 
Fit, a sudden state of unconsciousness and of contraction of the muscles 

lasting only a minute or two. Epilepsy is a kind of fit. 
Flex' or muscles (Lat. fleet ere, to bend), muscles which bend 

the limbs. 
Fo'cus (Lat. focus, a fireplace), the point where rays of light come 

together when passed through a lens. 
Food, anything which is assimilated by the body, and gives it weight, 

heat, or energy. The term includes water and mineral matter as 

well as vegetable and animal substances. 
Front'al (Lat. frons, the forehead), pertaining to the region of the skull 

or brain behind the forehead. 
Ful'crum (Lat. word meaning a prop), the fixed support around which 

a lever turns. 

Gall {gawl), a name applied to the bile while it is stored in the bag 

under the liver. 
Gan'gli-on (Gr. gagglion, a knot), a collection of nerve cells in the 

sympathetic system. Each looks like a grain kernel. 
Gas' trie (Gr. gaster, stomach), pertaining to the stomach. 
Gelatine {jel'a-tin) (Lat. gelare, to harden), a kind of albumin which 

forms the principal part of connective tissue. It will dissolve in 

hot water, and forms a jellylike or solid mass when cold. Glue is 

an impure form. 



GLOSSARY 411 

Germs {hz.i. germen. a bud), a name loosely applied to bacteria. 

Gizzard, the muscular organ in a fowPs abdomen which grinds food to 
pieces and acts in place of teeth. 

Gland (Lat. glans, an acorn), a collection of microscopic tubes which 
form a watery substance within the body. 

Glucose (Gr. glukus, sweet), a form of sugar found in the grape, and 
produced artificially by the action of sulphuric acid on starch ; it is 
also produced in the body by the action of the digestive fluids upon 
starch and sugar. 

Glu'ten (Lat. gluten, glue), the albumin of grain. 

Gly-co-chol'ic acid (Gr. glukits, sweet, and chole, bile), one of the prin- 
cipal waste substances in the bile. 

Gly'co-gen (Gr. ghikus, sweet, and genein, to generate), a form of 
sugar to which digested sugar and starch is turned by the liver. 

Gout igowt) (Lat. gutta, a drop), a swelling of a joint, especially of the 
great toe, caused by a disturbance of digestion and oxidation. It 
was formerly supposed to be due to a fluid or humor which flowed 
down in drops from the upper parts of the body. 

Grippe (g^P) (Fr. grippe, influenza), a kind of fever which occurs in 
epidemics. It is caused by the growth of a germ in the body. 

Hash'eesh, the gum of a kind of hemp. It produces an excited and 
dreamy state of mind. 

Ha-ver'si-an canals, the minute tunnels in bone through which the 
arteries rim. They were discovered by Havers, an English physi- 
cian, who lived in the seventeenth century. 

Hem-o-glo'bin (Gk. haima, blood, and Lat. globus, a ball), the coloring 
matter of the red blood cells. 

Hem-o-phil'i-a (Gr. haima, blood, and philein, to love), a state of the 
blood in which it will not clot. 

Hem'or-rhage (Gr. haima, blood, and rhegfiunai, to break), a flow of 
blood from a blood tube. 

Hi-ber-na'tion (Lat. hibernus, wintr}-), passing the winter in a torpid 
state, as frogs and snakes do. 

Hu'mer-us (Lat. humerus), the long bone in the upper part of the arm. 

Humors (Lat. /f/^wf^r, moisture), substances which were formerly sup- 
posed to circulate in the blood and to cause disease. 

Hy-dro-chlor'ic acid, a compound oi hydrogen and chlorine, commonly 
called muriatic acid. It is a violent poison. 



412 GLOSSARY 

Hy-dro-gen (hy'dro-jen) (Gr. hudor, water, and genein, to generate), a 
light, colorless gas . When ignited it unites with oxygen to form water. 

Hygiene {hy'ji-een) (Gr. hugieinos, healthy), the science which tells 
how to keep living bodies in good working order. 

Hy-po-der'mic injection (Gr. hupo, under, and derma, skin), the intro- 
duction of a solution under the skin by means of a hollow needle 
and syringe. The solution fills the lymph spaces and is absorbed 
into the capillaries or enters the circulation by way of the 
lymph . 

Hys-te'ri-a, a nervous disease in which there is great lack of self-con- 
trol. The sufferer easily gives way to the emotions, and especially 
to those of sorrow or mirth. 

H'e-um (Gr. eileiit, to twist), the lower half of the small intestine. 

In-ci'sor teeth (Lat. incidere, to cut into), the teeth in front, with which 
food is bitten into. 

Incus {in'kiis) (Lat. inais^ anvil), the middle bone of the chain in the 
ear drum, which transmits waves of sound from the drumhead to 
the inner ear. 

In-fec'tious disease (Lat. in, in, and facere^ to make), a disease which 
has for its cause some matter which can multiply and grow when 
introduced into the body of a healthy man. 

In-flam-ma'tion (Lat. in, in, and fla7nma, a flame), redness, swelling, 
pain, and increased heat in a part as a result of injury. It is nature's 
attempt to repair the part. Often it goes on to form matter. 

In-san'i-ty (Lat. in, not, and sanus, safe), unsoundness of mind per- 
sisting for a considerable time. 

In-spi-ra'tion (Lat. in, in, and spirare, to breathe), taking a breath 
into the lungs. 

In-tem'per-ance (Lat. in, not, and temperare, to regulate), gratifica- 
tion of a desire which does not denote a real need of the body. 

In-tes'tine (Lat. intus, within), the long tube in the abdomen in which 
digestion of food is completed after it leaves the stomach. 

In-tox-i-ca'tion (Lat. in, in, and toxiami, poison), great mental excite- 
ment or lack of control, usually due to alcohol. 

I'ris (Gr. iris, rainbow), the colored curtain in the eye behind the cornea. 

Jaundice {jahn'dis) (Yr. j'aune, yellow), yellowness of the skin due to 
a deficient excretion of bile by the liver. 



GLOSSARY 413 

Je-ju'num (Lat. jejunus^ empty), the middle portion of the small 

intestine. 
Joint {\j^\. jiDigere^ to join), the union of two bones. 

Kid'ney. the organ which excretes urea. 

Lab'y-rinth (Gr. laburinthos'), an intricate arrangement of passages. 

The inner ear. 
Lach'ry-mal glands (Lat. lacrinta, a tear), the glands which produce 

the tears. They are situated in the orbit just above the eyeball, upon 

its outer side. 
Lac'te-al tubes (Lat. lac, milk), the fine lymphatic tubes which take 

up fat from the intestine. During digestion they can be seen as 

milky lines across the mesentery. 
Lac-tom'e-ter (Lat. lac, milk, and w^/r?^;;/, measure) , an instrument for 

testing the purity of milk. 
Larynx {lah' rinks) (Gr. larngx), the box in the upper part of the neck 

in which the windpipe begins. It contains the vocal cords. 
Lau'da-num, opium dissolved in nine times its weight of alcohol. 
Lens (Lat. lois, lentil), a transparent substance having curved surfaces. 

It has the power of changing the directions of rays of light. 
Leu-co-ma-ine {Jew-ko' 7nah-i)i) (Gr. leukojna, white), a class of sub- 
stances resembling alkaloids which are found in the body during 

life. They are very poisonous, and much sickness is due to their 

presence. 
Lev'er (Fr. lever, to raise), a pry ; a rigid bar, one part of which is made 

to turn about a fixed point called a fulcrum, while an opposite part 

presses against a resisting object which it moves. 
Lig'a-ment (Lat. ligare, to bind), the fibrous bands of connective 

tissue which bind bones together to form joints. 
Liv'er. the large red gland in the upper right side of the abdomen. It 

forms bile and changes digested food to blood. 
Lymph (Lat. lympha, a spring of water), the plasma and white cor- 
puscles which have left the capillaries to nourish the cells of the 

body. 
Lym-phat'ics, the tubes which convey lymph back to the veins. Lymph 

nodes are spongy bodies like grains of wheat which strain out waste 

or poisonous substances from the lymph. In the neck and groin 

they can be felt, and are usually called kernels. 



414 GLOSSARY 

Ma-la'ri-a (Ital. malo, bad, and aria^ air), a disease caused by exhala- 
tions which arise from decaying vegetable matter. 
Malle-US (Lat. malleus, hammer), the first bone of the chain of small 

bones which conveys sound waves across the tympanum. 
Malt, grain, usually barley, soaked in water until it has sprouted about 

half an inch, and then dried. The sprouting changes a large part 

of the starch to sugar. 
Ma'ni-a (Lat. mania, r^ge), a form of insanity in which the intellect 

is so active that the judgment cannot control it. 
Mar'row, fat which fills the hollow bones. 
Mas-ti-ca'tion (Lat. masticare, to chew), properly, the grinding to 

which food is subjected by the teeth, tongue, and lips. Usually the 

mixing with the saliva is also included. 
Mas'toid process (Gr. mastos, the breast), the rounded projection of 

bone situated behind the ear. 
Me-dul'la oblongata (Lat. medulla, marrow), the part of the brain just 

above the spinal cord. It controls respiration and the contraction 

of arteries. 
Mel-an-choli-a (Gr. melas, black, and chole, bile), a form of insanity 

in which a person's mental actions are excessively retarded. He 

feels downcast and thinks every one is avoiding him on account 

of his sins. It is the opposite of mania. It was formerly supposed 

to be due to black bile circulating in the blood. 
Mem'brane (Lat. metnbrana, skin), any skin-like part of the body. 

The membrana tympani is the skin-like tissue which separates the 

middle ear from the outer ear. 
Mer'cu-ry (Lat. Mercurius, the messenger of the gods), the liquid 

metal commonly called quicksilver. 
Mes'en-ter-y (Gr. mesos, middle, and enter on, intestine), the thin fold 

of peritoneum which holds the intestine in place. 
Met-a-car'pal bones (Gr. meta, after, and karpos, the wrist), the five 

slender bones just below the wrist which form the palm of the 

hand. 
Met-a-tar'sal bones (Gr. meta, after, and tarsos, the flat of the foot), 

the five long bones in front of the ankle which form the front part 

of the foot. 
Mi'crobes (Gr. mih'os, little, and bios, life), the smallest living being. 

Microbes are plants, some of which may grow in the human body 

and produce diseases. They are the same as bacteria and germs. 



GLOSSARY 415 

Mi'cro-scope (Gr. jnikros^ little, and skopein^ to see), an instrument 
which makes minute objects appear large. 

Milk, the tiuid which all female mammals secrete for the nourishment 
of their young. 

Mi'tral (Gr. ^nitra, a head covering), the valve between the left auricle 
and ventricle ; when closed it resembles a priest's miter or hat. 

Molar (Lat. mala, a mill), a tooth having a flat surface for grinding 
food. The last three teeth on each side of each jaw are molars. 

Mold, a low order of microscopic plants which usually grow in the in- 
terior of substances. Common forms send up spore stalks which 
form the velvety coating popularly called mold. 

Mor-phine' (Gr. ?no?-pheus, the god of sleep), the principal alkaloid of 
opium. 

Mo'tor nerves (Lat. 7nove?'e, to move), the nerves which carry orders 
from the brain or spinal cord to cause the cells of the body to act. 

Mu'cous mem'brane, the soft, skin-like membrane lining cavities which 
open upon the surface of ih^ body. 

Mu'cus (Lat. iniicus)^ the thin, slimy fluid produced by the epithelium 
lining the organs of digestion and respiration. 

Mu-ri-at'ic acid (Lat. viuria. brine), the common name of hydro- 
chloric acid. The acid is very sour and corrosive. It combines 
with sodium to form common salt, but many of its combinations 
are poisonous. 

Mus'cle (Lat. musculus, a little mouse), a collection of cells which can 
become thicker and shorter and so produce motion. 

Nar-cot'ic (Gr. narkoiin. to benumb), a substance which hinders the 

action of nerves and nerve cells and produces sleep. 
Na'sal duct (Lat. 7iasa, the nose), the duct which carries tears from 

the eyes to the nose. 
Nerve (Gr. neuron, nerve), a collection of the threads which conduct 

impulses between the cells of the body and the central nervous 

system. 
Neuritis {neiv-ri' tis) (Gr. neuron, nerv^e), inflammation of a nerve. 
Neu'tral-ize (Lat. neuter^ neither), to make neither acid nor alkaline. 
Nic'o-tine, the active principle in tobacco, named from the Frenchman 

Nicot who introduced tobacco into France in 1560. 
Nu'cle-o albumin, a form of albumin containing iron and found in the 

nucleus of cells. From it hemoglobin is formed. 



41 6 GLOSSARY 

Nu'cle-us (Lat. micleus, kernel), a mass usually distinguishable near the 
center of each cell. It seems to be endowed with special vital powers. 

Oc-cip'i-tal region (Lat. ob^ against, and caput ^ the head), the region 
of the skull or brain which is situated farthest back. 

0-le-o-mar'ga-rine, a compound made from beef fat and milk. It has 
the properties and nutritive value of butter. 

01-fac'to-ry (Lat. olere^ to have a smell, and facer e^ to make), pertain- 
ing to the sense of smell. 

0-men'tum (Lat. omentunt)^ the fatty apron in front of the intes- 
tine. 

O'pi-um (Gr. opion, poppy juice), the dried juice of a kind of poppy 
growing in western Asia. It is a narcotic and is used to produce 
sleep and to benumb pain. 

Op'tic (Gr. optikos)^ pertaining to sight. The optic nerves convey 
impressions of sight. The optic tubercles are collections of gray 
matter in the brain between the medulla and cerebrum. They are 
reflex centers for the eye. 

Or'bit (Lat. orbis, a circle), the bony cavity which contains the 
eyeball. 

Or'gan (Gr. organon, a tool), a collection of tissues having a definite 
compact form and purpose. 

Or-gan'ic (Gr. organon, a tool), a term designating a substance built 
up only by the agency of living substances. 

Ox-i-da'tion, the union of oxygen with another substance. It is the 
essential part of the processes of burning and of breathing. 

Oxygen {ox'y-jeii) (Gr. oxtts^ sharp or acid, and genein, to generate), a 
gas forming one fifth of the air. Its union with the cells of the 
body forms the essential part of the process of breathing. 

O'zone (Gr. ozon^ smelling), a very active form of oxygen formed by 
electricity and sometimes found in the air. 

Pal'ate (Lat. palatuni)^ the roof of the mouth. 

Pal-pi-ta'tion (Lat. palpitare^ to throb), violent throbbing of the 

heart, so that its beats make themselves felt through the chest wall. 
Pan'cre-as (Gr. pan, all, and kreas, flesh), the gland situated behind 

the stomach which forms the pancreatic juice. The sweetbread. 
Pan-cre-at'ic juice, the liquid secretion of the pancreas which digests 

albumin, fat, and sugar in the intestine. 



GLOSSARY 417 

Pan'ic (Gr. to panikon^ from Pan, the god of the woods, and of sudden 

fear), a sudden and infectious fear which sometimes seizes upon a 

crowd. 
Pa-pilla (Lat. papilla^ pimple), a minute projection of the true skin 

into the epidermis. It contains the endings of the nerves of 

touch. 
Pa-ral'y-sis (Gr. para, beside, and luein, to loosen), lack of action of 

a part due usually to a failure of the motor nerves to bring the im- 
pulses for action. 
Par-e-gor'ic (Gr. paregoros, soothing), a sweet-tasting mixture coritain- 

ing opium and used chiefly in quieting children. 
Pa-ri'e-tal bones (Lat. paries, a wall), the top and sides of the 

skull. 
Pa-ro'tid glands (Gr. para, near, and ous, ear), the salivary glands in 

the front of the ear. 
Pel'vis (Lat. pelvis, basin), the massive ring of bone which forms the 

hips. Its cavity is somewhat larger than a large tea cup and con- 
tains some of the intestine. 
Pep'sin (Gr. peptein, to cook or digest), a lifeless ferment found in the 

stomach of all animals. It digests albumin. 
Pep'tone (Gr. peptos, cooked), the form to which albumin is changed 

by digestion. 
Per-i-car'di-um (Gr. peri, around, and kardia, heart), the thin bag 

which surrounds the heart. 
Per-i-os'te-um (Gr. peri, around, and osteon, bone), the thin, tough 

membrane which covers bone, reproduces its cells, and transmits its 

blood vessels and nerves. 
Per-i-stal'sis (Gr. peri, around, and stellein, to arrange), the regular, 

worm-like movements of the alimentary canal, which force its con- 
tents onward. 
Per-i-to-ne'um (Gr. peri, around, and teinein, to stretch), the thin, 

shining membrane which lines the interior of the abdomen and 

covers its organs. 
Per-spi-ra'tion {'L^X. per, through, and spirare, to breathe), the watery 

secretion of the skin. The sweat. 
Pha-lan'ges (Gr. phalagx, a rank of soldiers), the rows of bone which 

form the fingers and toes. Its singular is phalanx. 
Pharynx {far' inks) (Gr. pharugx, the throat, from pharein, to cleave), 

the cavity back of the nose and mouth, 
ov. PHYSIOL. — 27 



41 8 ^ GLOSSARY 

Phos'phor-US (Gr. phos^ light, and pherein^ to bring), a waxy, yellowish 
substance which combines with oxygen at ordinary temperatures, 
giving off heat and a faint light. The light produced by rubbing 
matches is due to the phosphorus. 

Phys-i-ol'o-gy (Gr. phusis, nature, and logos, discourse), the science 
which tells of the working of living bodies. 

Pi-a ma-ter (Lat. pia, pious, and jnater, mother), the delicate cover- 
ing of the brain which carries its blood vessels, in distinction from 
the thick protecting dura mater. 

Plas'ma (Gr. plasma, molded), the liquid part of blood in distinction 
from the cells which float in it. It is composed chiefly of water, 
albumin, and minerals. It is food for the cells of the body and it 
washes away their waste matters. 

Pleura {plew'ra) (Gr. pleura, rib), the lining of the chest and coating 
of the lung. 

Plex'us (Lat. pled ere, to braid), a network of sympathetic nerve cells 
and fibers. 

Plumb'ing (Lat. plumbum, lead), the pipes which conduct water and 
sewage in a house. Many are made of lead. 

Pneumonia (jiew-?no'ni-a) (Gr. pneumon, a lung), a disease in which 
the air sacs of the lung become filled with coagulated matters from 
the blood. 

Poi'son (Lat. potto, a drink), a substance which destroys or interferes 
with the life of the cells, when it is taken into the body. 

Por'tal vein (Lat. porta, a gate), the vein formed by the union of the 
veins from the digestive organs. This vein divides into the capilla- 
ries of the liver. Finally three veins conduct the blood to the ascend- 
ing vena cava. 

Pro'tO-plasm (Gr. protos, first, 2Mdi plasma, form), the albuminous sub- 
stance which forms the body of every living cell. 

Proximate principles, the elementary substances existing as such in 
the body. 

Ptomaine {to' mah-iit) (Gr. ptojna, a. dead body), a class of poison- 
ous substances resembling alkaloids and leucomaines, which are 
found in dead bodies. Their presence makes decayed food 
dangerous. 

Ptyalin {ti'a-lUi) (Gr. ptuein, to spit), the lifeless ferment in the saliva 
which changes starch to sugar. 

Pul'mo-na-ry (Lat. pulmo, lung), pertaining to the lungs. 



GLOSSARY 419 

Pulse (Lat. pidsus, a blow), the wave which may be felt in an artery 

with each heart beat. 
Pu'pil (Lat. pitpilla), the opening in the iris through which light enters 

the eve. It appears as a round black spot in the center of the col- 
ored part of the eye. 
Pus (Lat. puteo, to rot), the creamy matter which flows from an abscess. 

It is formed mostly of dead white blood cells. 
Pu-tre-fac'tion {\^2X. putris, rotten, and /<7<:^;v, to make), the process 

of decay accompanied by bad odors. 
Py-lo'nis (Gr. pule, a gate), the orifice in the right end of the stomach, 

through which food passes into the intestine. 
Py'ri-dine (Gr. ptir, fire), a poisonous substance formed by burning 

nicotine. 

Ra'di-us (Lat. radius, the spoke of a wheel), the bone upon the thumb 

side of the arm, below the elbow. 
Re'flex action (Lat. r<?, back. 2ind fleet ere, to turn), the action of the 

central nerve cells in sending orders for motion in response to 

an impulse brought by sensory nerves. 
Ren'nin. a lifeless ferment extracted from the lining of the fourth 

stomach of a calf, and used to curdle milk in cheese making. 

The same ferment is found in the human stomach, especially in 

infancy. 
Res-pi-ra'tion (Lat. re, again, and spirare, to breathe), the process of 

breathing and of the interchange of oxygen and carbonic acid gas 

in the cells of the body. 
Ret'i-na (Lat. rete, a net), the inner lining of the eye in which the 

nerves of sight end. 
Rheumatism {ru' tna-tis7ti) (Gr. rheum, a flowing or stream), a swell- 
ing of the joints in which they are often quickly affected one after 

another. Usually it is due to fluid collecting in the bag of the 

synovial membrane. 
Rick'ets, a disease in which the bones have too little lime and bend too 

easily. 

Sa'crum (Lat. sacer, sacred, for the bone was offered in sacrifice), the 
part of the backbone which completes the pelvis behind. 

Sa-li'va (Lat. saliva; Gr. sialon, spittle), the watery fluid in the 
mouth. 



420 GLOSSARY 

Sa-pon-i-fi-ca'tion (Lat. sapo, soap, and facere, to make), the process 
of making soap. Commonly the name soap is applied only to the 
combination of soda or potash with the acid part of fat. But lime, 
or magnesium, or other metal may take the place of soda or potash, 
as it does when hard water and soap are used to wash the hands. 
The lime soap which is formed feels sticky and rough, and does not 
dissolve in water, but forms a white scum on the surface. 

Scap-u-la (Lat. scapulae^ the shoulder blades), the flat bone upon the 
back behind the shoulder. The shoulder blade. 

Sciatica {si-at'i-kd) (Gr. ischiadikos, pertaining to the hip), a painful 
inflammation of the main nerve of the leg which begins just behind 
the hip joint. 

Sclerotic {skler-ot'ic) (Gr. skleros, hard), the tough outer covering of 
the eyeball. 

Scur'vy, the disease caused by lack of variety of food. It consists of 
pain and of bleeding under the skin, especially of the legs and gums. 

Sebaceous glands {se-ba' shus) (Lat. sebufn, fat), the glands in the skin 
which secrete oil. 

Se-cre'tion (Lat. secretus. separated), a substance which is separated 
from the blood by the epithelium of glands and used by the body. 

Sem-i-cir'cu-lar canals, the three tunnels in the inner ear in which there 
are nerves whose duty is to take note of the position of the body in 
balancing itself. 

Sem-i-lu'nar valves, three half-moon-shaped valves at the beginning 
both of the aorta and of the pulmonary artery. They prevent blood 
from flowing back to the heart. 

Sen-sa'tion (Lat. sentire, to feel), a conscious impression made upon 
the brain by an impulse brought by a sensory nerve. 

Sen'so-ry nerves (Lat. sentire^ to feel), nerves which carry impulses 
from the cells to the central nervous s)^stem. 

Se'rous membrane, the thin membrane lining the cavities of the body 
which do not connect with its surface. It is named from the fluid, 
like serum, which forms in it in a quantity just sufficient for lubri- 
cation. 

Se'rum (Lat. serum, the watery part of curdled milk), the straw-colored 
liquid which separates from a blood clot. 

Sewer {su'er), an underground tunnel for carrying slops from the houses 
of a town. 

Si'nus (Lat. sinus, curve), a cavity. 



GLOSSARY 421 

Skel'e-ton (Gr. skellein, to dry), the bones of the body. 
So-lu'tion (Lat. solutus, dissolved), a Hquid mixture in which the in- 
gredients are not changed in essential properties. 
Speech, the expression of thoughts by words. 
Spine (Lat. spi?ia, the backbone), the backbone. 
Spleen (Gr. splen), a soft, red organ lying to the left of the stomach. 

Its use is probably to form the red blood cells. 
Spore (Gr. spora, seed), a reproductive cell of a flowerless plant. Spores 

are extremely minute, and some are capable of resisting influences 

which are fatal to most other forms of life. 
Stapes (Lat. stapes, stirrup), the third bone in the chain of bones which 

conducts sound from the membrana tympani to the inner ear. 
Starch (Anglo-Saxon, slearc, strong), a food substance composed of 

carbon, hydrogen, and oxygen. It is the first recognizable form 

through which organic substances pass as they are built up by plants. 

In the body it is changed to sugar. 
Ste-ap'sin (Gr. siear, suet), the ferment of the pancreatic juice which 

digests fat. 
Ster'il-ize (Lat. sterilis, without power to produce seed), to destroy 

bacteria and their spores as by heat or chemicals. It is usually 

applied to the preparation of surgical dressings. 
Ster'num (Gr. sternon, the breast), the flat bone which extends down 

the front of the breast ; the breast bone. 
Stim'u-lant (Lat. stimulus, a whip), a substance which excites a part 

to action without increasing its supply of energy. 
Stomach {stum'ak) (Gr. stoma, a mouth or entrance), the muscular 

bag into which food enters when swallowed, and which begins the 

work of digestion. 
Strych'nine (Gr. struchnos, a kind of shrub), a substance obtained from 

the seeds of the strychnos shrub. It is used to increase the power of 

the nervous system ; in overdoses.it produces violent convulsions. 
Sub-lin'gual glands (Lat. sub, under, and lingua, tongue), the two 

salivary glands under the front part of the tongue. 
Sub-max'il-la-ry gland (Lat. sub, under, and maxilla, jaw), the 

salivary gland situated under the side of the lower jaw. 
Su'gar (Lat. saccharum, sugar), a sweet substance composed of carbon, 

hydrogen, and oxygen in nearly the same proportions as in starch. 

There are many varieties, but during digestion all are changed to 

glucose or grape sugar. It gives heat to the body. 



422 GLOSSARY 

Syl'vi-an fissure, the deep fissure extending backward upon each side 

of the brain. It was named after the French physician Sylvius, who 

died in 1555. 
Sym-pa-thet'ic system, the collection of nerve cells and nerves which 

control the preparation of food and its distribution to the cells. It 

is subordinate to the spinal cord. 
Syn-o'vi-a, the fluid which lubricates the movable joints. 
Syn-o'vi-al membrane, the membrane lining the movable joints. 
Sys'tem (Gr. simistanai, to place together), a series of tissues and 

organs, working together for a definite purpose. 
Sys'to-le (Gr. sun, together, and stelleln, to set), the contraction of 

the heart forcing blood into the arteries of the body. 

Tan'nin (Fr. tan, originally meaning oak), an acid found in the barks 
of most trees, and used to toughen and harden skins into leather. 

Tape worm, a kind of worm inhabiting the intestine. It resembles a 
long piece of white tape. 

Tar'sal bones (Gr. tarsos, the sole of the foot), the eight irregularly 
shaped bones in the hinder half of the foot. 

Tar'tar, a kind of hard, brown substance which often forms upon the teeth. 

Tau-ro-chol'ic acid, one of the waste substances in the bile. 

Tem'po-ral (Lat. iempora, the temples), pertaining to the regions of 
the skull in the neighborhood of the ears. 

Ten'don (Lat. tendere, to stretch), a strong white cord, one end of 
which is attached to a muscle above a joint, and the other to a bone 
or to flesh below a joint. 

Thoracic duct, the tube running upward upon the backbone and con- 
veying lymph to the veins. 

Tho'rax (Gr. thorax, breastplate), the cavity of the body under the 
ribs. 

Thy'roid (Gr. thiireos, a shield, and eidos, form). The large folded 
cartilage which forms the principal part of the larynx. 

Tib'i-a (Lat. tibia), the shin bone. 

Tissue {ti'shii), a group of cells or fibers alike in form and action. 

To-bac'co (West Indian tabaco, the name of the pipe used in smoking), 
a narcotic plant used for smoking and for chewing. 

Ton'sil (Lat. tonsilla'), a round body situated one on each side of the 
throat in front of the pharynx. They have no special use. Some- 
times they become enlarged, and need to be removed. 



GLOSSARY 423 

Tox'in (Gr. toxikon, arrow poison), a virulent poison formed within a 
living body. Most toxins are ptomaines. 

Trache-a (Gr. trachiis, rough), the windpipe; rings of cartilage make 
its outside irregular and rough. 

Trans-fusion (Lat. trans, across, ^.ndfinidere, to pour out), transferring 
blood from the veins of one person into the veins of another. 

Tri'ceps (Lat. tri, three, and caput, head), the muscle extending down 
the back of the arm from the shoulder to the elbow. It straightens 
the elbow. Its upper end has three branches. 

Trichinae {trick-i' nee) (Gr. thrix, a hair), microscopic worms which 
live in the muscles of a pig. They sometimes remain alive in par- 
tially cooked pork, and if eaten produce a deadly disease. 

Tri-cus'pid valve (Lat. tres, three, and cuspis, point), the valve between 
the right auricle and ventricle ; it is formed of three leaves. 

Tryp-sin (Gr. tribeiJi, to rub), the ferment of the pancreatic juice which 
digests albumin. 

Tu-ber-cu-lo'sis (Lat. tubercidum, a little lump), a disease in which 
small white lumps like pinheads form in the flesh. Later, these 
soften and run out as matter. The disease is commonly called con- 
sumption. 

Tym'pa-num (Lat. tynnpamun, drum), the middle ear. 

Ty'phoid fever (Gr. tuphos, a cloud, and hence a stupor arising from 
fever, and eidos, form), a tedious and weakening fever caused by the 
growth of a kind of bacteria. 

Ty-ro-tox'i-con (Gr. turos, cheese, and toxicon, poison), a virulent 
ptomaine poison sometimes found in cheese and other substances 
made from milk. 

Ul'na (Lat. ulna, the elbow), the bone on the little finger side of the 

lower arm. 
U're-a (Gr. ouron, urine), a very soluble crystalline substance, one of 

the three principal waste products of the body. It is the essential 

part of urine. 
U-re'ter (Gr. ouron, urine), the tube leading from the kidney to the 

bladder. 

Vac-cin-a'tion (Lat. vacca, a cow), the introduction of the germs of 
cowpox into the skin for the purpose of causing the disease as a 
protection against smallpox. 



424 GLOSSARY i* 

Valv'u-lae con-ni-ven'tes (Lat. valvulae, little sliding doors, and conni- 
ventes, winking), deep puckers in the mucous membrane of the 
small intestine. 

Var'i-cose veins (Lat. varix, an enlarged vein)j distended and enlarged 
veins. 

Vas-o-mo'tor nerves (Lat. vasa, a vessel, and motor, pertaining to 
motion), nerves which produce either contraction or dilatation of the 
arteries. 

Vein {vane) (Lat. vena, a vein), a tube which carries blood back to 
the heart. 

Ven-ti-la'tion (Lat. vent Hare, to winnow), changing the air of a room. 

Ven'tri-cle (Lat. ventriculus, stomach), one of the large, thick-walled 
cavities of the heart. 

Ven-triro-quism (Lat. venter, the abdomen, and loqtii, to speak), 
speaking so that the voice seems to come from a distance away 
from the speaker. 

Ver'mi-form ap-pen'dix (Lat. vermis, worm, appendix, something 
added), the closed tube, shaped like an earthworm, which projects 
from the beginning of the large intestine. In some of the lower 
animals, as in the hen, it is as large as the other part of the intes- 
tine, but in man is only about two inches in length and one eighth 
inch in diameter. 

Ver'te-bra (Lat. vertebra), a joint of the backbone. 

Vest'i-bule (Lat. vestibulum, a porch or entrance), the cavity of the 
internal ear from which the cochlea and semicircular canals extend. 

Villus (Lat. villus, a tuft of hair), one of the minute slender projections 
upon the inner surface of the intestine. 

Vin'e-gar, a sour liquid made from wine or cider by the oxidation of its 
alcohol to acetic acid, of which it contains from two to four per cent. 

Vit're-ous hu'mor (Lat. vitrum, glass), the jelly-like fluid which fills 
the eyeball behind the lens. 

X rays, a form of radiant energy discovered by Roentgen in 1895. It 
penetrates wood, flesh, and many other substances which are opaque 
to sunlight. 

Yeast, a collection of single-celled plants, whose growth changes sugar 
to alcohol and carbonic acid gas. The agent which causes bread to 
become light. 



INDEX 



Abdomen, 66. 
Abscess, 395. 
Absorption, 89, 260. 
Accommodation, 339. 
Achilles' tendon, 374. 
Acid, 28, 149. 
Aconite, 148, 151. 
Adam's apple, 349. 
Adenoid vegetations, 193, 327. 
Adulteration, of alcohol, 47. 
of coffee, 127. 
of milk. III. 
Air, 206, 220. 
in lungs, 207. 
in clothing, 238. 
moisture in, 236. 
rarefied, 222. 
sacs, 195. 
Albumin, 23, 34, 69, 84, 92. 
Alcohol, 44, 140. 

effects on arteries, 189. 

brain, 315. 

digestion, 98. 

excretion, 251. 

habit, 319. 

heart, 168. 

heat, 243. 

heredity, 319. 

intestine, ICXD. 

judgment, 316. 

kidney, 251. 

liver, 100. 

lungs, 213. 

muscle, 377. 

nerves, 273. 

paralysis, 317. 

peristalsis, 99. 

respiration, 214. 

sight, 342. 

stomach, 99. 

voice, 354. 



Alimentary canal, 53. 
Alkalies, 28, 149. 
Alkaloids, 152. 
Ameba, 10. 
Amylopsin, 84. 
Anaesthesia, 146, 223, 320. 
Anatomy, 9. 
Anemia, 159. 
Antidote, 149. 
Antimony, 151, 
Antiseptics, 387. 
Antitoxin, 386. 
Antrum, 54, 193, 324. 
Aorta, 172. 
Apoplexy, 311. 
Appendicitis, 80. 
Appendix, vermiform, 80. 
Appetite, 74. 
Aqueous humor, 334, 
Argon, 220. 
Arsenic, 150. 

Arterial blood, 157, 177, 207= 
Artery, 163, 172, 187. 
Asphyxia, 212. 
Assimilation, 91. 
Astigmatism, 340. 
Auricle, 163. 

Bacteria, 384. 

Barley, 122. 

Bathing, 261. 

Beans, 122. 

Beard, 261. 

Beds, 240. 

Beef tea, 115. 

Beer, 43. 

Belladonna, 152. 

Biceps, 375. 

Bicuspid tooth, 55. 
j Bile, 84, 85, 93. 
I Biliousness, 85, 93. 



425 



426 



INDEX 



Bilirubin, 250. 
Biscuit, 121. 
Bitters, 101. 
Blackheads, 259. 
Bladder, 84, 249. 
Bleeding, 186. 
Blister, 257. 
Blood, 156, 206. 

as food, 1 1 7. 

in lower animals, 159. 

poisoning, 389. 
Blowing, 198. 
Boards of health, 389. 
Bones, 357. 

Bowels, regularity of, 94. 
Brain, 289. 

food, 133, 309. 

in lower animals, 300. 
Bread, 43, 121, 122. 
Breathing, 192, 198. 
Bright's disease, 249. 
Broken, back, 281. 

bones, 361. 
Bronchi, 195. 
Bunion, 366. 
Burns, 242. 
Butter, III. 
Butterine, 112. 

Caecum, 80. 

Caisson, 222. 

Cake, 121. 

Callus, 257. 

Cancellous bone, 359. 

Canine teeth, 54. 

Cannabis indica, 145. 

Canned food, 42, 125. 

Capillary, 173, 208. 

Carbolic acid, 150, 388. 

Carbon, 33, 36. 

Carbonic acid gas, 33, 206, 208, 223. 

Cardiac, 67. 

Carpal bones, 358. 

Cartilage, 360. 

Caseine, 109. 

Cataract, 340. 

Catarrh, 61. 

Cellar air, 224. 

Cells, II, 13,92, 174, 393. 

Cellulose, 26. 

Cement, 55. 

Cerebellum, 292. 



Cerebrum, 293. 
Cesspool, 252. 
Cheeks, 56. 
Cheese, no. 
Chemical action, 28. 
Chicory, 127. 
Chill, 234. 
Chloral, 145. 
Chloride of lime, 388. 
Chloroform, 146, 320. 
Chlorophyll, 35. 
Choking, 199. 
Cholera, 385. 
Choroid coat, 334. 
Chyle, 86. 
Chyme, 69. 
Cigar, 141. 
Cigarette, 142. 
Cilia, 195, 197, 205, 218. 
Circulation, 177. 

in lower animals, 180. 
Clabber, no. 
Clams, 116. 
Clavicle, 358. 
Clothing, 237. 
Clot, 158. 
Coagulation, 23. 
Coal gas, 225. 
Cocaine, 145. 
Coccyx, 357. 
Cochlea, 326. 
Cocoa, 127. 
Coffee, 126. 
Cold, sensation of, 234. 

feet, 239. 

taking, 185, 396. 
Colon, 80. 
Color, blindness, 337. 

and heat, 238. 

of skin, 257. 
Complexion, 259. 
Condensed milk, 112. 
Congestion, 185, 393. 
Conjunctiva, 336. 
Connective tissue, 11, 38, 394. 
Conservation of energy, 36. 
Consonants, 352. 
Consumption, see Tuberculosis. 
Contagious diseases, 385. 
Contraction of muscles, 373. 
Convolutions of ]:)rain, 293. 
Cooking, 51, 123. 



INDEX 



427 



Copper, 150. 
Corn meal, 122. 
Cornea, 335. 
Corns, 257. 
Corpuscles, 156. 
Cotton, 237. 
Coughing, 198. 
Crabs, 1 17. 
Cranial nerves, 290. 
Cricoid cartilage, 349. 
Crown of tooth, 55. 
Crying, 198. 
Cud, 104. 

Curvature of spine, 366. 
Cuticle, 257. 
Cutis, 256. 

Deafness, 327. 
Decay, 13, 24, 42, 46, ^^4 
Decayed food, 152. 
Deglutition, 6i. 
Delirium, 31 1. 

tremens, 318. 
Dentine, 55. 
Derma, 256. 
Diaphragm, 66, 196. 
Diastole of heart, 165. 
Diet list, 132. 
Diffusion, 24. 
Digestibility of food, 108. 
Digestion, 51. 

in lower animals, 104. 
Diphtheria, 385. 
Disease, 148. 

of bone, 361. 

of eye, 341. 

of heart, 167. 

of hip joint, 368. 

of spine, 28 1. 

germs, 226, 385. 
Dislocations, 367, 
Distillation, 44. 
Dreams, 308. 
Dropsy, 180. 
Drowning, 213. 
Drugs, 148. 
Duodenum, 80. 
Dura mater, 290. 
Dust, 221. 
Dyspepsia, 74, 93. 

Ear, 325. 
wax, 329. 



Ear, in lower animals, 329. 
Eating, 76, 132. 
Eggs, 112. 
Electric shock, 213. 
Emergencies — 

Alcoholic paralysis, 141, 317. 

Apoplexy, 311. 

Asphyxia, 212. 

Bleeding, 186. 

Broken bones, 361. 

Burns, 242. 

Choking, 199. 

Coal gas, 225. 

Cold, taking, 185. 

Contagious diseases, 385. 

Dislocation of bones, 367. 

Drowning, 213. 

Electric shock, 213. 

Fainting, 150, 168. 

Fever, 233, 242, 263. 

Fits, 312. 

Fright, 312. 

Frozen limbs, 241. 

Hysteria, 309, 

Insanity, 310. 

Panics, 312. 

Poisoning, 144, 149. 

Sprains of joints, 367. 

Stings, 154. 

Sunstroke, 236. 
Emulsion, 25. 
Enamel, 55. 
Energy, conservation of, 36. 

source of, 233. 
Epidermis, 257. 
Epiglottis, 61. 
Epilepsy, 312. 
EpitheUum, 57, 58, 68, 82, 248, 

261, 271, 394. 
Erysipelas, 385, 389. 
Esophagus, 62. 
Ether, 320. 
Eustachian tube, 327. 
Excretion, 248. 
Exercise, 166, 309, 377. 
Exhaustion of retina, 337. 
Expansion of lung, 197. 
Expiration, 196. 
Extensor muscles, 375. 
Eye. 334- 

in lower animals, 344. 
Eyelids, 336. 



257. 



428 



INDEX 



Face, 376. 
Fainting, 150, 168. 
Far sight, 339. 
Fat, 25, 34, 91, 209. 
Fatty heart, 167. 
Femur, 358. 

Fermentation, 42, 76, lOO, 109. 
Fever, 233, 242, 263. 
Fibrin, 158. 
Fibula, 359. 
Field of view, 337. 
Filtration, 137. 
of air, 229. 
Fissures of brain, 293. 
Fish, 116. 
Fits, 312, 
Flat foot, 359. 
Flexor muscles, 375. 
Fluids of body, 15. 
Focus, 18. 

Food, 51, 107, 120, 131. 
Foul air, 223. 
Freckles, 257. 
Frontal region, 294. 
Frozen limbs, 241. 
Fruit, 124. 
Fulcrum, 373. 
Fur, 238. 
Fusel oil, 45. 

Gall bladder, 84. 

Ganglia, 284. 

Gaping, 198. 

Gastric juice, 68. 

Gelatine, 23. 

Germs, no, 384. 

Gills, 216. 

Gizzard, 105. 

Gland, 57. 

Glucose, 51, 92. 

Glue, 23. 

Gluten, 120. 

Glycocholic acid, 250. 

Glycogen, 92. 

Goose flesh, 259. 

Gout, 367. 

Grain, 120. 

Gray matter, 276, 290, 292, 293. 

Grippe, 385. 

Habit, 142, 306. 
Hair, 259. 
Hangnail, 261. 



Hasheesh, 145. 

Haversian canals, 360. 

Headache, 95, 340. 

Heart, 162. 

Heat, 34, 233. 

Hemoglobin, 24, 156, 207. 

Hemophilia, 159. 

Hemorrhage, 186. 

Heredity, 306. 

Hibernation, 243. 

Hiccough, 198. 

Hip, 358. 

Hip joint disease, 368. 

History of circulation, 181. 

Humerus, 358. 

Humors, 159. 

Hunchback, 368. 

Hunger, 269. 

Hydrochloric acid, 68. 

Hydrogen, ^s- 

Hygiene, 9. 

Hypodermic injections, 153, 180. 

Hysteria, 309. 

Ileum, 80. 

Illusions, of hearing, 329. 

of sight, 342. 
Incisor, 54. 
Incus, 326. 
Indigestion, 73, 93. 
Infectious diseases, 385. 
Inflammation, 393. 
Ingrowing nail, 261. 
Insalivation, 53. 
Insanity, 310. 
Inspiration, 196. 
Instincts, 268. 
Intellect, 299. 

Intemperance in eating, 75, loi, 251. 
Intensity of voice, 351. 
Intestinal juice, 84. 
Intestine, 79, 
Intoxication, 214, 317. 
Iris, 335- 
Iron, 24, 124. 
Itching, 271. 
Ivory, 55. 

Jaundice, 250. 
Jaws, 54. 
Jejunum, 80. 
Joints, 364^ 



INDEX 



429 



Kidneys, 249. 

Labyrinth, 325. 
Lachrymal gland, 336. 
Lacing, tight, 200. 
Lacteal, 91. 
Lactometer, 11 1. 
Larynx, 194, 349. 
Laudanum, 144. 
Laughing, 198. 
Lead, 136, 150. 
Lens, S33- 
Leucomaines, 152. 
Levers, 373. 
Life, 9. 12, 38, 398. 
Ligaments, 365. 
Light, 333- 
Lime, 28. 
Lips, 56. 

Liver, 82, 93, 250. 
Living rooms, 236. 
Lobsters, 117. 
Lungs, 192. 
Lymph, 178. 
Lymphatics, 174, 178. 
Lymph nodes, 178. 

Malaria, 225. 
Malleus, 126. 
Malt, 43. 
Mania, 310. 
Marrow, 160, 359. 
Mastication, 60. 
Mastoid, 327. 
Meat, 113. 

Medulla oblongata, 290. 
Melancholia, 311. 
Membrane, 327. 
Memory, 295, 297. 
Mercury, 150, 388. 
Mesentery, 79. 
Metacarpal bones, 358. 
Metals, 150. 
Metatarsal bones, 359. 
Microbes, 384. 
Microscope, 16. 
Milk, 109. 

Mind, stimulation of, 305. 
Minerals, 27, 33, 51. 
Mitral valve, 164. 
Molar teeth, 55. 
Mold, 383. 



Morphine, 144, 
Motor, region, 296, 

center, 278, 296. 

nerves, 271. 
Mouth, 53. 

breathing, 193, 353. 
Mucous membrane, 57. 
Miiller's fluid, 72. 
Muriatic acid, 363. 
Muscles, 366, 371, 376. 
Muscular sense, 271. 
Mushroom, 152. 

Nails, 259. 
Narcotics, 140, 150. 
Nasal duct, 336. 
Near sight, 339. 
Nerve cells, 276. 
Nerves, 266. 

of heart, 166. 

motor, 271. 

sensory, 268. 

sympathetic, 285. 
Nervousness, 309. 
Neuritis, 273. 
Neutralize, 28. 
Nicotine, 141. 
Night air, 225. 
Nose, 192, 324. 
Nucleo-albumin, 24, 1260 
Nucleus, II, 12, 24. 
Nuts, 125. 

Oatmeal, 122. 
Occipital region, 295. 
Occupation diseases, 221. 
Odors, 224. 
Oleomargarine, 112. 
Olfactory nerves, 325. 
Omentum, 80. 
Opium, 143, 320. 
Optic, nerve, 334. 
tubercles, 292. 
Orbit, 336. 

Organic substances, 37. 
Organs, 16. 

Oxidation, S3^ 46, 209, 233, 243. 
Oxygen, 33, 131, 207, 212, 221. 
Oysters, 116. 
Ozone, 220. 

Pain, 270. 
Palate, 53. 



430 



INDEX 



Palpitation of heart, i66, 167. 

Pancakes, 121. 

Pancreas, 82. 

Pancreatic juice, 84. 

Panics, 312. 

Paper clothing, 239. 

Papilla, 258. 

Paralysis, 272. 

Paregoric, 144. 

Parietal region, 294. 

Parotid gland, 59. 

Patella, 359, 375. 

Paunch, 104. 

Peas, 122. 

Pelvis, 358. 

Pepsin, 69. 

Peptone, 24, 69, 92. 

Pericardium, 162. 

Periosteum, 359, 360. 

Peristalsis, 63, 69, 85. 

Peritoneum, 66. 

Perspiration, 235, 248. 

Phalanges, 359. 

Pharynx, 61, 193. 

Phosphorus, 151. 

Physiology, 9. 

Pia mater, 290. 

Pitch of voice, 350. 

Plants and animals, 37. 

Plasma, 157. 

Play, 378. 

Pleura, 196. 

Plexus, 285. 

Plumbing, 253. 

Pneumogastric nerve, 291. 

Pneumonia, 397. 

Poisoning, 149. 

Portal, circulation, 177. 

vein, 92. 
Potash, 28. 
Potatoes, 122. 
Poultice, 396. 
Protoplasm, 1 1. 
Proud flesh, 258, 394. 
Proximate principles, 22. 
Ptomaines, 153, 384. 
Ptyalin, 59. 

Pulmonary circulation, 176. 
Pulse, 173. 
Pupil, 335. 

Purification of air, 230. 
Pus, 395. 



Putrefaction, see Decay. 
Pylorus, 67. 
Pyridine, 142. 

Quality of voice, 351. 

Radius, 358. 

Reaction of bath, 262. 

Reconstruction after oxidation, 35. 

Red blood cells, 157. 

Reflex action, 278. 

Regions of brain, 294. 

Rennin, 69. 

Repair, of injuries, 393. 

in blood tubes, 188. 

in nerves, 273. 
Respiration, 175, 192, 208, 217. 

artificial, 202. 

in lower animals, 215. 
Respiratory center, 201, 211, 291. 
Retina, 334. 
Rheumatism, 367. 
Ribs, 357. 
Rice, 122. 
Rickets, 361. 
Ringworm, 384. 
Root beer, 48. 
Round shoulders, 377. 
Rumen, 104. 

Sacrum, 357. 
Saliva, 59. 
Salt, 27. 

Saponification, 26, 85. 
Scapula, 358. 
Scar, 394. 
Sciatica, 273. 
Sclerotic coat, 334. 
Scrofula, 179. 
Scurvy, 126. 
Seasonings, 126. 
Sebaceous glands, 259. 
Secretion, 58, 272. 
Semicircular canals, 326. 
Semilunar valve, 164. 
Sensation, 268. 
Sensibilities, 299. 
Sensory regions, 295. 
Serous membrane, 67. 
Serum, 158. 
Sewage, 251. 
Sewer, 252. 



INDEX 



431 



Sewer gas, 224, 252. 

Shortness of breath, 211. 

Sick room, 388. 

Sighing, 199. 

Sight, 335. 

Silk, 238. 

Silver, 150. 

Sinus, 324. 

Site for house, 253. 

Skeleton, 357. 

Skin, 256. 

grafting, 258. 
Sleep, 307. 
Smell, 325. 
Smoking, 141. 
Smothering, 199. 
Snake bites, 153. 
Sneezing, 198. 
Snoring, 198. 
Snuff, 142. 
Soap, 26. 
Sobbing, 198. 
Soda, 28. 
Solar plexus, 285. 
Solution, 22. 
Sounds, of heart, 166. 

of breathing, 198. 
Soup, 115. 
Specimens, 19, 72. 
Speech, 297, 351, 
Spinal, column, 357. 

cord, 276. 

nerves, 277. 
Spitting, 199. 
Spleen, 160. 
Spores, 383. 
Sprains, 367. 
Standing, 375. 
Stapes, 326. 
Starch, 26, 35, .84. 
Starvation, 133. 
Steapsin, 85. 
Sterilization, 387. 
Sternum, 357. 
Stimulants, 126, 168. 
Stings, 154. 
Stomach, 67. 
Strychnine, 150. 
Subcutaneous tissue, 256. 
Sublingual gland, 59. 
Submaxillary gland, 59. 
Sucking, 199. 



Suffocation, 199. 
Sugar, 26, 35, 132, 209. 
Summer complaint, no. 
Sun in plant growth, 36. 
Sunstroke, 236. 
Swallowing, 62. 
Sylvian fissure, 293. 
Sympathetic system, 284. 
Synovial membrane, 365. 
Systems, 16. 
Systole of heart, 165. 

Tannin, 127. 
Tapeworm, 117. 
Tarsal bones, 359. 
Tartar, 56. 
Taste, 74, 323. 
Taurocholic acid, 250. 
Tea, 126. 
Tears, 336. 
Teeth, 54. 

Temperance drinks, 48. 
Temperature, of body, 233. 
in lower animals, 243. 
sense, 234, 270. 
Temporal region, 294. 
Tendon, 372. 
Thirst, 47, 269. 
Thoracic duct, 91, 179. 
Thorax, 196. 
Thought regions, 297. 
Thyroid cartilage, 349. 
Tibia, 359. 
Tickling, 271. 
Tissues, 14. 
Tobacco, 141. 

effects on brain, 319. 

heart, 169. 

lungs, 215. 

sight, 342. 

smell, 325. 

voice, 353. 
Tongue, 57, 352. 
Tonsil, 193. 
Touch, 269, 323. 
Toxins, 384. 
Trachea, 194. 
Triceps, 375. 
Trichinae, 1 17. 
Tricuspid valve. 164. 
Trypsin, 84. 
Tuberculosis, 1 1 7, 226, 368, 389. 



432 



INDEX 



Tusk, 55. 
Tympanum, 327. 
Typhoid fever, no, 385. 
Tyrotoxicon, 153. 

Ulna, 358. 

Unconscious mind action, 307. 

Urea, 34, 248. 

Ureter, 249. 

Urine, 249. 

Vaccination, 387. 
Vagus nerve, 291. 
Valves of heart, 164. 
Valvulse conniventes, 81. 
Varicose veins, 189. 
Vasomotor, center, 291. 

nerves, 185. 
Vegetables, 124. 
Veins, 163, 175. 
Venous blood, 157, 177, 20 
Ventilation, 226. 
Ventricle, of brain, 294. 

of heart, 163. 
Ventriloquism, 341. 



Vermiform appendix, 80. 
Vertebra, 357. 
Vestibule, 325. 
Villi, 81. 
Vinegar, 41. 
Vitreous humor, 334. 
Vocal cords, 350. 
exercise, 353. 
Voice, 194, 349. 
Vovi^els, 352. 

Walking, 376. 

Wart, 258. 

Water, 22, ^3, 135- 

White blood cells, 157, 174, 386, 393. 

matter, 276, 290, 293. 

swelling, 368. 
Will, 299. 
Wine, 44. 
Wood, 26, 38. 
Wool, 237. 

X rays, 342. 

Yavs^ning, 198. 
Yeast, 41, 382. 



m 30 1904 



